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  • Pointer Implementation Details in C

    - by Will Bickford
    I would like to know architectures which violate the assumptions I've listed below. Also I would like to know if any of the assumptions are false for all architectures (i.e. if any of them are just completely wrong). sizeof(int *) == sizeof(char *) == sizeof(void *) == sizeof(func_ptr *) The in-memory representation of all pointers for a given architecture is the same regardless of the data type pointed to. The in-memory representation of a pointer is the same as an integer of the same bit length as the architecture. Multiplication and division of pointer data types are only forbidden by the compiler. NOTE: Yes I know this is nonsensical. What I mean is - is there hardware support to forbid this incorrect usage? All pointer values can be casted to a single integer. In other words, what architectures still make use of segments and offsets? Incrementing a pointer is equivalent to adding sizeof(the pointed data type) to the memory address stored by the pointer. If p is an int32* then p+1 is equal to the memory address 4 bytes after p. I'm most used to pointers being used in a contiguous, virtual memory space. For that usage, I can generally get by thinking of them as addresses on a number line. See (http://stackoverflow.com/questions/1350471/pointer-comparison/1350488#1350488).

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  • Using Partitions for a large MySQL table

    - by user293594
    An update on my attempts to implement a 505,000,000-row table on MySQL on my MacBook Pro: Following the advice given, I have partitioned my table, tr: i UNSIGNED INT NOT NULL, j UNSIGNED INT NOT NULL, A FLOAT(12,8) NOT NULL, nu BIGINT NOT NULL, KEY (nu), key (A) with a range on nu. nu ought to be a real number, but because I only have 6-d.p. accuracy and the maximum value of nu is 30000. I multiplied it by 10^8 made it a BIGINT - I gather one can't use FLOAT or DOUBLE values to PARTITION a MySQL table. Anyway, I have 15 partitions (p0: nu<25,000,000,000, p1: nu<50,000,000,000, etc.). I was thinking that this should speed up a typical to SELECT: SELECT * FROM tr WHERE nu>95000000000 AND nu<100000000000 AND A.>1. to something of the order of the same query on a table consisting of only the data in the relevant partition (<30 secs). But it's taking 30mins+ to return rows for queries within a partition and double that if the query is for rows spanning two (contiguous) partitions. I realise I could just have 15 different tables, and query them separately, but is there a way to do this 'automatically' with partitions? Has anyone got any suggestions?

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  • Allow paste in worksheet without overwriting locked cells

    - by jjeaton
    I have a protected worksheet that users would like to copy and paste into. I have no control over the workbook they are copying from. The protected worksheet has some rows that are available for data entry, and other rows that are locked and greyed out to the user. The users would like to be able to paste over the top of the entire worksheet from another random workbook and have all the cells available for data entry filled in, while the locked cells are undisturbed. In the current state, the user gets an error when they try to paste, because it cannot paste over the locked cells. Example: Worksheet 1: Act1 100 100 100 Act2 100 100 100 Act3 100 100 100 Worksheet 2: (The second row is locked) Act1 300 300 300 Act2 200 200 200 Act3 100 100 100 After copying/pasting Worksheet 2 should look like this: Act1 100 100 100 Act2 200 200 200 Act3 100 100 100 The values from worksheet 1 are populated and the locked rows are undisturbed. I've been thinking along the lines of having a hook where on paste, the locked cells are unlocked so that the paste can happen, and then are reverted to their original values and relocked. Is there some way I can loop through the cells in the clipboard and only paste cells where the target isn't locked? It is preferable to not create a separate button for paste, so there is less impact on the users, but if that's the only way, I'm not opposed to it. Currently, I plan on grouping the locked rows together, so that the data entry cells are contiguous, but then the accounts will be out of order, which is not preferred.

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  • C#: Take Out Image Portion of JPEG to Backup Metadata?

    - by Carlo Mendoza
    This will be a little backwards from the typical approach. I've used ExifTool for metadata manipulation before, but I really want to keep the best metadata backup I can before I make anything permanent. What I want to do is remove the compressed image portion of a JPEG file to leave everything else intact. That's backing up EXIF, Makernotes, IPTC, XMP, etc whether at the beginning or end of the file. What I've tried so far is to strip all metadata from a copy of the original JPEG, and use it as a basis of what bytes will be taken out of the original. After looking at the raw data, it doesn't seem like the stripped copy is contiguous in the original copy. There may be some header information still remaining in the stripped version. I don't really know. Not a good way to do it, I suppose. Are there any markers that will absolutely tell me where the compressed JPEG image data starts and ends? I understand that JPEG files have 0xFFD8 and 0xFFD9 to mark the start and end of the image, but have come to find out that metadata is actually between those markers. I'm using C#. Thank you.

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  • Shall this Regex do what I expect from it, that is, matching against "A1:B10,C3,D4:E1000"?

    - by Will Marcouiller
    I'm currently writing a library where I wish to allow the user to be able to specify spreadsheet cell(s) under four possible alternatives: A single cell: "A1"; Multiple contiguous cells: "A1:B10" Multiple separate cells: "A1,B6,I60,AA2" A mix of 2 and 3: "B2:B12,C13:C18,D4,E11000" Then, to validate whether the input respects these formats, I intended to use a regular expression to match against. I have consulted this article on Wikipedia: Regular Expression (Wikipedia) And I also found this related SO question: regex matching alpha character followed by 4 alphanumerics. Based on the information provided within the above-linked articles, I would try with this Regex: Default Readonly Property Cells(ByVal cellsAddresses As String) As ReadOnlyDictionary(Of String, ICell) Get Dim validAddresses As Regex = New Regex("A-Za-z0-9:,A-Za-z0-9") If (Not validAddresses.IsMatch(cellsAddresses)) then _ Throw New FormatException("cellsAddresses") // Proceed with getting the cells from the Interop here... End Get End Property Questions 1. Is my regular expression correct? If not, please help me understand what expression I could use. 2. What exception is more likely to be the more meaningful between a FormatException and an InvalidExpressionException? I hesitate here, since it is related to the format under which the property expect the cells to be input, aside, I'm using an (regular) expression to match against. Thank you kindly for your help and support! =)

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  • R selecting duplicate rows

    - by Matt
    Okay, I'm fairly new to R and I've tried to search the documentation for what I need to do but here is the problem. I have a data.frame called heeds.data in the following form (some columns omitted for simplicity) eval.num, eval.count, ... fitness, fitness.mean, green.h.0, green.v.0, offset.0, green.h.1, green.v.1,...green.h.7, green.v.7, offset.7... And I have selected a row meeting the following criteria: best.fitness <- min(heeds.data$fitness.mean[heeds.data$eval.count = 10]) best.row <- heeds.data[heeds.data$fitness.mean == best.fitness] Now, what I want are all of the other rows with that have columns green.h.0 to offset.7 (a contiguous section of columns) equal to the best.row Basically I'm looking for rows that have some of the conditions the same as the "best" row. I thought I could just do this, heeds.best <- heeds.data$fitness[ heeds.data$green.h.0 == best.row$green.h.0 & ... ] But with 24 columns it seems like a stupid method. Looking for something a bit simpler with less manual typing. Thanks!

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  • How to index a table with a Type 2 slowly changing dimension for optimal performance

    - by The Lazy DBA
    Suppose you have a table with a Type 2 slowly-changing dimension. Let's express this table as follows, with the following columns: * [Key] * [Value1] * ... * [ValueN] * [StartDate] * [ExpiryDate] In this example, let's suppose that [StartDate] is effectively the date in which the values for a given [Key] become known to the system. So our primary key would be composed of both [StartDate] and [Key]. When a new set of values arrives for a given [Key], we assign [ExpiryDate] to some pre-defined high surrogate value such as '12/31/9999'. We then set the existing "most recent" records for that [Key] to have an [ExpiryDate] that is equal to the [StartDate] of the new value. A simple update based on a join. So if we always wanted to get the most recent records for a given [Key], we know we could create a clustered index that is: * [ExpiryDate] ASC * [Key] ASC Although the keyspace may be very wide (say, a million keys), we can minimize the number of pages between reads by initially ordering them by [ExpiryDate]. And since we know the most recent record for a given key will always have an [ExpiryDate] of '12/31/9999', we can use that to our advantage. However... what if we want to get a point-in-time snapshot of all [Key]s at a given time? Theoretically, the entirety of the keyspace isn't all being updated at the same time. Therefore for a given point-in-time, the window between [StartDate] and [ExpiryDate] is variable, so ordering by either [StartDate] or [ExpiryDate] would never yield a result in which all the records you're looking for are contiguous. Granted, you can immediately throw out all records in which the [StartDate] is greater than your defined point-in-time. In essence, in a typical RDBMS, what indexing strategy affords the best way to minimize the number of reads to retrieve the values for all keys for a given point-in-time? I realize I can at least maximize IO by partitioning the table by [Key], however this certainly isn't ideal. Alternatively, is there a different type of slowly-changing-dimension that solves this problem in a more performant manner?

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  • Implementing list position locator in C++?

    - by jfrazier
    I am writing a basic Graph API in C++ (I know libraries already exist, but I am doing it for the practice/experience). The structure is basically that of an adjacency list representation. So there are Vertex objects and Edge objects, and the Graph class contains: list<Vertex *> vertexList list<Edge *> edgeList Each Edge object has two Vertex* members representing its endpoints, and each Vertex object has a list of Edge* members representing the edges incident to the Vertex. All this is quite standard, but here is my problem. I want to be able to implement deletion of Edges and Vertices in constant time, so for example each Vertex object should have a Locator member that points to the position of its Vertex* in the vertexList. The way I first implemented this was by saving a list::iterator, as follows: vertexList.push_back(v); v->locator = --vertexList.end(); Then if I need to delete this vertex later, then rather than searching the whole vertexList for its pointer, I can call: vertexList.erase(v->locator); This works fine at first, but it seems that if enough changes (deletions) are made to the list, the iterators will become out-of-date and I get all sorts of iterator errors at runtime. This seems strange for a linked list, because it doesn't seem like you should ever need to re-allocate the remaining members of the list after deletions, but maybe the STL does this to optimize by keeping memory somewhat contiguous? In any case, I would appreciate it if anyone has any insight as to why this happens. Is there a standard way in C++ to implement a locator that will keep track of an element's position in a list without becoming obsolete? Much thanks, Jeff

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  • When is the reintegrate option really necessary?

    - by Tor Hovland
    If you always sync a feature branch before you merge it back, why do you really have to use the --reintegrate option? The Subversion book says: When merging your branch back to the trunk, however, the underlying mathematics is quite different. Your feature branch is now a mishmosh of both duplicated trunk changes and private branch changes, so there's no simple contiguous range of revisions to copy over. By specifying the --reintegrate option, you're asking Subversion to carefully replicate only those changes unique to your branch. (And in fact, it does this by comparing the latest trunk tree with the latest branch tree: the resulting difference is exactly your branch changes!) So the --reintegrate option only merges the changes that are unique to the feature branch. But if you always sync before merge (which is a recommended practice, in order to deal with any conflicts on the feature branch), then the only changes between the branches are the changes that are unique to the feature branch, right? And if Subversion tries to merge code that is already on the target branch, it will just do nothing, right? In this blog post, Mark Phippard writes: http://blogs.open.collab.net/svn/2008/07/subversion-merg.html If we include those synched revisions, then we merge back changes that already exist in trunk. This yields unnecessary and confusing conflicts. Can somebody give me an example of when dropping reintegrate gives me unnecessary conflicts?

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  • Time gaps between host clEnqueue_xxx calls

    - by dialer
    Consider these OpenCL calls (3 memcpy DtoH, 4313 cl_float elements each): clEnqueueReadBuffer(CommandQueue, SpectrumAbsMem, CL_FALSE, 0, SpectrumMemSize, SpectrumAbs, 0, NULL, NULL); clEnqueueReadBuffer(CommandQueue, SpectrumReMem, CL_FALSE, 0, SpectrumMemSize, SpectrumRe, 0, NULL, NULL); clEnqueueReadBuffer(CommandQueue, SpectrumImMem, CL_FALSE, 0, SpectrumMemSize, SpectrumIm, 0, NULL, NULL); When I analyze these with the NVIDIA visual profiler, I see that the actual memcpy operation only takes 8 us, but there is a significant gap of around 130 us after each memcpy. I'm already using the supposedly asynchronous method (the CL_FALSE in the argument list). When I use only one operation, but with three times the size, the operation is way faster. Why is the time gap between the actual memcpy operations so huge, whereas the gap between the kernel execution (exactly before these three operations) and the first memcpy is only 7us? Can I get rid of it, or do I need to accumulate more data before starting a memcpy? If so, is there a convenient way how I could combine mutliple arrays into a single contiguous block of memory, but still have a cl_mem object as a separate device memory pointer to each section?

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  • Using MPI_Type_Vector and MPI_Gather, in C.

    - by Goloneg
    Hi, I am trying to multiply square matrices in parallele with MPI. I use a MPI_Type_vector to send square submatrixes (arrays of float) to the processes, so they can calculate subproducts. Then, for the next iterations, these submatrices are send to neighbours processes as MPI_Type_contiguous (the whole submatrix is sent). This part is working as expected, and local results are corrects. Then, I use MPI_Gather with the contiguous types to send all local results back to the root process. The problem is, the final matrix is build (obviously, by this method) line by line instead of submatrix by submatrix. I wrote an ugly procedure rearranging the final matrix, but I would like to know if there is a direct way of performing the "inverse" operation of sending MPI_Type_vectors (i.e., sending an array of values and directly arranging it in a subarray form in the receiving array). An example, to try and clarify my long text : A[16] and B[16] are 4x4 matrices to be multiplied ; C[16] will contain the result ; 4 processes are used (Pi with i from 0 to 3) : Pi gets two 2x2 submatrices : subAi[4] and subBi[4] ; their product is stored locally in subCi[4]. For instance, P0 gets : subA0[4] containing A[0], A[1], A[4] and A[5] ; subB0[4] containing B[0], B[1], B[4] and B[5]. After everything is calculed, root process gathers all subCi[4]. Then C[16] contains : [ subC0[0], subC0[1], subC0[2], subC0[3], subC1[0], subC1[1], subC1[2], subC1[3], subC2[0], subC2[1], subC2[2], subC2[3], subC3[0], subC3[1], subC3[2], subC3[3]] and I would like it to be : [ subC0[0], subC0[1], subC1[0], subC1[1], subC0[2], subC0[3], subC1[2], subC1[3], subC2[0], subC2[1], subC3[0], subC3[1], subC2[2], subC2[3], subC3[2], subC3[3]] without further operation. Does someone know a way ? Thanks for your advices.

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  • Algorithm: Find smallest subset containing K 0's

    - by Vishal
    I have array of 1's and 0's only. Now I want to find contiguous subset/subarray which contains at least K 0's. Example Array is 1 1 0 1 1 0 1 1 0 0 0 0 1 0 1 1 0 0 0 1 1 0 0 1 0 0 0 and K(6) should be 0 0 1 0 1 1 0 0 0 or 0 0 0 0 1 0 1 1 0.... My Solution Array: 1 1 0 1 1 0 1 1 0 0 0 0 1 0 1 1 0 0 0 1 1 0 0 Index: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Sum: 1 2 2 3 4 4 5 6 6 6 6 6 7 7 8 9 9 9 9 10 11 11 11 Diff(I-S): 0 0 1 1 1 2 2 2 3 4 5 6 6 7 7 7 8 9 10 10 10 11 12 For K(6) Start with 9-15 = Store difference in diff. Next increase difference 8-15(Difference in index) 8-14(Compare Difference in index) So on keep moving to find element with least elements... I am looking for better algorithm for this solution.

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  • Generating all unique crossword puzzle grids

    - by heydenberk
    I want to generate all unique crossword puzzle grids of a certain grid size (4x4 is a good size). All possible puzzles, including non-unique puzzles, are represented by a binary string with the length of the grid area (16 in the case of 4x4), so all possible 4x4 puzzles are represented by the binary forms of all numbers in the range 0 to 2^16. Generating these is easy, but I'm curious if anyone has a good solution for how to programmatically eliminate invalid and duplicate cases. For example, all puzzles with a single column or single row are functionally identical, hence eliminating 7 of those 8 cases. Also, according to crossword puzzle conventions, all squares must be contiguous. I've had success removing all duplicate structures, but my solution took several minutes to execute and probably was not ideal. I'm at something of a loss for how to detect contiguity so if anyone has ideas on this it'd be much appreciated. I'd prefer solutions in python but write in whichever language you prefer. If anyone wants, I can post my python code for generating all grids and removing duplicates, slow as it may be.

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  • Unix sort keys cause performance problems

    - by KenFar
    My data: It's a 71 MB file with 1.5 million rows. It has 6 fields All six fields combine to form a unique key - so that's what I need to sort on. Sort statement: sort -t ',' -k1,1 -k2,2 -k3,3 -k4,4 -k5,5 -k6,6 -o output.csv input.csv The problem: If I sort without keys, it takes 30 seconds. If I sort with keys, it takes 660 seconds. I need to sort with keys to keep this generic and useful for other files that have non-key fields as well. The 30 second timing is fine, but the 660 is a killer. More details using unix time: sort input.csv -o output.csv = 28 seconds sort -t ',' -k1 input.csv -o output.csv = 28 seconds sort -t ',' -k1,1 input.csv -o output.csv = 64 seconds sort -t ',' -k1,1 -k2,2 input.csv -o output.csv = 194 seconds sort -t ',' -k1,1 -k2,2 -k3,3 input.csv -o output.csv = 328 seconds sort -t ',' -k1,1 -k2,2 -k3,3 -k4,4 input.csv -o output.csv = 483 seconds sort -t ',' -k1,1 -k2,2 -k3,3 -k4,4 -k5,5 input.csv -o output.csv = 561 seconds sort -t ',' -k1,1 -k2,2 -k3,3 -k4,4 -k5,5 -k6,6 input.csv -o output.csv = 660 seconds I could theoretically move the temp directory to SSD, and/or split the file into 4 parts, sort them separately (in parallel) then merge the results, etc. But I'm hoping for something simpler since looks like sort is just picking a bad algorithm. Any suggestions? Testing Improvements using buffer-size: With 2 keys I got a 5% improvement with 8, 20, 24 MB and best performance of 8% improvement with 16MB, but 6% worse with 128MB With 6 keys I got a 5% improvement with 8, 20, 24 MB and best performance of 9% improvement with 16MB. Testing improvements using dictionary order (just 1 run each): sort -d --buffer-size=8M -t ',' -k1,1 -k2,2 input.csv -o output.csv = 235 seconds (21% worse) sort -d --buffer-size=8M -t ',' -k1,1 -k2,2 input.csv -o ouput.csv = 232 seconds (21% worse) conclusion: it makes sense that this would slow the process down, not useful Testing with different file system on SSD - I can't do this on this server now. Testing with code to consolidate adjacent keys: def consolidate_keys(key_fields, key_types): """ Inputs: - key_fields - a list of numbers in quotes: ['1','2','3'] - key_types - a list of types of the key_fields: ['integer','string','integer'] Outputs: - key_fields - a consolidated list: ['1,2','3'] - key_types - a list of types of the consolidated list: ['string','integer'] """ assert(len(key_fields) == len(key_types)) def get_min(val): vals = val.split(',') assert(len(vals) <= 2) return vals[0] def get_max(val): vals = val.split(',') assert(len(vals) <= 2) return vals[len(vals)-1] i = 0 while True: try: if ( (int(get_max(key_fields[i])) + 1) == int(key_fields[i+1]) and key_types[i] == key_types[i+1]): key_fields[i] = '%s,%s' % (get_min(key_fields[i]), key_fields[i+1]) key_types[i] = key_types[i] key_fields.pop(i+1) key_types.pop(i+1) continue i = i+1 except IndexError: break # last entry return key_fields, key_types While this code is just a work-around that'll only apply to cases in which I've got a contiguous set of keys - it speeds up the code by 95% in my worst case scenario.

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  • Determining the health of a Cisco switch port?

    - by ewwhite
    I've been chasing a packet-loss and network stability issue for a handful of end-users on an internal network for the past few days... These issues surfaced recently, however, the location was struck by lightning six weeks ago. I was seeing 5-10% packet loss between a stack of four Cisco 2960's and several PC's and phones on the other side of a 77-meter run. The PC's were run inline with the phones over a trunked link. We were seeing dropped calls and interruptions in client-server applications and Microsoft Exchange connectivity. I tried the usual troubleshooting steps remotely, having a local technician do the following during breaks in user and production activity: change cables between the wall jack and device. change patch cables between the patch panel and switch port(s). try different switch ports within the 2960 stack. change end-user devices with known-good equipment (new phones, different PC's). clear switch port interface counters and monitor incrementing errors closely. (Pastebin output of sh int) Pored over the device logs and Observium RRD graphs. No link up/down issues from the switch side. change power strips on the end-user side. test cable runs from the Cisco 2960 using test cable-diagnostics tdr int Gi4/0/9 (clean)* test cable runs with a Tripp-Lite cable tester. (clean) run diagnostics on the switch stack members. (clean) In the end, it took three changes of switch ports to find a stable solution. The only logical conclusion is that a few Cisco 2960 switch ports are bad or flaky... Not dead, but not consistent in behavior either. I'm not used to seeing individual ports die in this manner. What else can I test or check to determine if these devices are bad? Is it common for single ports to have problems, rather than a contiguous bank of ports? BTW - show cable-diagnostics tdr int Gi4/0/14 is very cool... Interface Speed Local pair Pair length Remote pair Pair status --------- ----- ---------- ------------------ ----------- -------------------- Gi4/0/14 1000M Pair A 79 +/- 0 meters Pair B Normal Pair B 75 +/- 0 meters Pair A Normal Pair C 77 +/- 0 meters Pair D Normal Pair D 79 +/- 0 meters Pair C Normal

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  • Is my Cisco switch port bad?

    - by ewwhite
    I've been chasing a packet-loss and network stability issue for a handful of end-users on an internal network for the past few days... These issues surfaced last week, however the location was struck by lightning six weeks ago. I was seeing 5-10% packet loss between a stack of four Cisco 2960's and several PC's and phones on the other side of a 77-meter run. The PC's were run inline with the phones over a trunked link (switchport configuration pastebin). We were seeing dropped calls and interruptions in client-server applications and Microsoft Exchange connectivity. I tried the usual troubleshooting steps remotely, having a local technician do the following during breaks in user and production activity: change cables between the wall jack and device. change patch cables between the patch panel and switch port(s). try different switch ports within the 2960 stack. change end-user devices with known-good equipment (new phones, different PC's). clear switch port interface counters and monitor incrementing errors closely. (Pastebin output of sh int) Pored over the device logs and Observium RRD graphs. No link up/down issues from the switch side. change power strips on the end-user side. test cable runs from the Cisco 2960 using test cable-diagnostics tdr int Gi4/0/9 (clean)* test cable runs with a Tripp-Lite cable tester. (clean) run diagnostics on the switch stack members. (clean) In the end, it took three changes of switch ports to find a stable solution. The only logical conclusion is that a few Cisco 2960 switch ports are bad or flaky... Not dead, but not consistent in behavior either. I'm not used to seeing individual ports die in this manner. What else can I test or check to determine if these devices are bad? Is it common for single ports to have problems, rather than a contiguous bank of ports? BTW - show cable-diagnostics tdr int Gi4/0/14 is very cool... Interface Speed Local pair Pair length Remote pair Pair status --------- ----- ---------- ------------------ ----------- -------------------- Gi4/0/14 1000M Pair A 79 +/- 0 meters Pair B Normal Pair B 75 +/- 0 meters Pair A Normal Pair C 77 +/- 0 meters Pair D Normal Pair D 79 +/- 0 meters Pair C Normal

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  • Missing startup screens and slow bootup/login after using WinClone to expand Bootcamp partition

    - by user26453
    I used WinClone to backup my Bootcamp partition, which was a Windows 7 Ultimate install, on my late 2006 Macbook Pro. I desired to expand the Bootcamp partition's size. It worked reasonably well with some hiccups along the way and some remaining issues. First issue I ran into was the Bootcamp Assistant utility - it would not recreate the partition. This was due to a lack of contiguous space that is required for the Bootcamp partition. As a result I wiped the whole drive and reinstalled Snow Leopard, did the minimum amount of system updates, and created and formated a new Bootcamp partition. WinClone restored the image without complaint and the image was automatically resized to the new partition's size. Second issue I ran into was after the first boot into Windows. The first thing I noticed was that instead of the newer "slick" startup screen (4 colors wisping around, a Windows 7 title), there was more of an old school style startup screen (a progress bar with block increments, yellow/greenish color, nothing else really). The initial bootup to a login screen was slow, perhaps as Windows dealt with the partition changes. After logging in, the screen goes blank and the computer seems to hang for a minute, before completing the login. After subsequent restarts, the slick screen is still missing, boot to login screen is normal, but the time from login to desktop active is still very slow. As a side note, this behavior of a long time from login to the desktop finally loaded I've previously only seen when the computer would try to hibernate and fail (battery is really bad). On the next startup, I would see this behavior, but not subsequently. So a potential cause: I imaged the partition after hibernating out of Windows. From reading some posts/guides on the subject, this was not recommended, and perhaps shouldn't even have worked? Could the partition be stuck in some weird mode as a result that makes the boot issues appear? I've attempted to disable hibernation and restart, trying to delete the .sys file that hibernation uses. Other fixes I'm thinking of attempting are booting a Win7 disc and repairing the install/partition. I can't shake the nagging feeling something isn't right as a result of the modified boot screens and the slow login process.

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  • Management and Monitoring Tools for Windows Azure

    - by BuckWoody
    With such a large platform, Windows Azure has a lot of moving parts. We’ve done our best to keep the interface as simple as possible, while giving you the most control and visibility we can. However, as with most Microsoft products, there are multiple ways to do something – and I’ve always found that to be a good strength. Depending on the situation, I might want a graphical interface, a command-line interface, or just an API so I can incorporate the management into my own tools, or have third-party companies write other tools. While by no means exhaustive, I thought I might put together a quick list of a few tools you can use to manage and monitor Windows Azure components, from our IaaS, SaaS and PaaS offerings. Some of the products focus on one area more than another, but all are available today. I’ll try and maintain this list to keep it current, but make sure you check the date of this post’s update – if it’s more than six months old, it’s most likely out of date. Things move fast in the cloud. The Windows Azure Management Portal The primary tool for managing Windows Azure is our portal – most everything you need is there, from creating new services to querying a database. There are two versions as of this writing – a Silverlight client version, and a newer HTML5 version. The latter is being updated constantly to be in parity with the Silverlight client. There’s a balance in this portal between simplicity and power – we’re following the “less is more” approach, with increasing levels of detail as you work through the portal rather than overwhelming you with a single, long “more is more” page. You can find the Portal here: http://windowsazure.com (then click “Log In” and then “Portal”) Windows Azure Management API You can also use programming tools to either write your own interface, or simply provide management functions directly within your solution. You have two options – you can use the more universal REST API’s, which area bit more complex but work with any system that can write to them, or the more approachable .NET API calls in code. You can find the reference for the API’s here: http://msdn.microsoft.com/en-us/library/windowsazure/ee460799.aspx  All Class Libraries, for each part of Windows Azure: http://msdn.microsoft.com/en-us/library/ee393295.aspx  PowerShell Command-lets PowerShell is one of the most powerful scripting languages I’ve used with Windows – and it’s baked into all of our products. When you need to work with multiple servers, scripting is really the only way to go, and the Windows Azure PowerShell Command-Lets allow you to work across most any part of the platform – and can even be used within the services themselves. You can do everything with them from creating a new IaaS, PaaS or SaaS service, to controlling them and even working with security and more. You can find more about the Command-Lets here: http://wappowershell.codeplex.com/documentation (older link, still works, will point you to the new ones as well) We have command-line utilities for other operating systems as well: https://www.windowsazure.com/en-us/manage/downloads/  Video walkthrough of using the Command-Lets: http://channel9.msdn.com/Events/BUILD/BUILD2011/SAC-859T  System Center System Center is actually a suite of graphical tools you can use to manage, deploy, control, monitor and tune software from Microsoft and even other platforms. This will be the primary tool we’ll recommend for managing a hybrid or contiguous management process – and as time goes on you’ll see more and more features put into System Center for the entire Windows Azure suite of products. You can find the Management Pack and README for it here: http://www.microsoft.com/en-us/download/details.aspx?id=11324  SQL Server Management Studio / Data Tools / Visual Studio SQL Server has two built-in management and development, and since Version 2008 R2, you can use them to manage Windows Azure Databases. Visual Studio also lets you connect to and manage portions of Windows Azure as well as Windows Azure Databases. You can read more about Visual Studio here: http://msdn.microsoft.com/en-us/library/windowsazure/ee405484  You can read more about the SQL tools here: http://msdn.microsoft.com/en-us/library/windowsazure/ee621784.aspx  Vendor-Provided Tools Microsoft does not suggest or endorse a specific third-party product. We do, however, use them, and see lots of other customers use them. You can browse to these sites to learn more, and chat with their folks directly on how they support Windows Azure. Cerebrata: Tools for managing from the command-line, graphical diagnostics, graphical storage management - http://www.cerebrata.com/  Quest Cloud Tools: Monitoring, Storage Management, and costing tools - http://communities.quest.com/community/cloud-tools  Paraleap: Monitoring tool - http://www.paraleap.com/AzureWatch  Cloudgraphs: Monitoring too -  http://www.cloudgraphs.com/  Opstera: Monitoring for Windows Azure and a Scale-out pattern manager - http://www.opstera.com/products/Azureops/  Compuware: SaaS performance monitoring, load testing -  http://www.compuware.com/application-performance-management/gomez-apm-products.html  SOASTA: Penetration and Security Testing - http://www.soasta.com/cloudtest/enterprise/  LoadStorm: Load-testing tool - http://loadstorm.com/windows-azure  Open-Source Tools This is probably the most specific set of tools, and the list I’ll have to maintain most often. Smaller projects have a way of coming and going, so I’ll try and make sure this list is current. Windows Azure MMC: (I actually use this one a lot) http://wapmmc.codeplex.com/  Windows Azure Diagnostics Monitor: http://archive.msdn.microsoft.com/wazdmon  Azure Application Monitor: http://azuremonitor.codeplex.com/  Azure Web Log: http://www.xentrik.net/software/azure_web_log.html  Cloud Ninja:Multi-Tennant billing and performance monitor -  http://cnmb.codeplex.com/  Cloud Samurai: Multi-Tennant Management- http://cloudsamurai.codeplex.com/    If you have additions to this list, please post them as a comment and I’ll research and then add them. Thanks!

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  • FAT Volume and CE

    - by Kate Moss' Open Space
    Whenever we format a disk volume, it is a good idea to name the label so it will be easier to categorize. To label a volume, we can use LABEL command or UI depends on your preference. Windows CE does provide FAT driver and support various format (FAT12, FAT16,FAT32, ExFAT and TFAT - transaction-safe FAT) and many feature to let you scan and even defrag the volume but not labeling. At any time you format a volume in CE and then mount it on PC, the label is always empty! Of course, you can always label the volume on PC, even it is formatted in CE. So looks like CE does not care about the volume label at all, neither report the label to OS nor changing the label on FAT.So how can we set the volume label in CE? To Answer this question, we need to know how does FAT stores the volume label. Here are some on-line resources are handy for parsing FAT. http://en.wikipedia.org/wiki/File_Allocation_Table http://www.pjrc.com/tech/8051/ide/fat32.html http://www.microsoft.com/whdc/system/platform/firmware/fatgen.mspx You can refer to PUBLIC\COMMON\OAK\DRIVERS\FSD\FATUTIL\MAIN\bootsec.h and dosbpb.h or the above links for the fields we discuss here. The first sector of a FAT Volume (it is not necessary to be the first sector of a disk.) is a FAT boot sector and BPB (BIOS Parameter Block). And at offset 43, bgbsVolumeLabel (or bsVolumeLabel on FAT16) is for storing the volume lable, but note in the spec also indicates "FAT file system drivers should make sure that they update this field when the volume label file in the root directory has its name changed or created.". So we can't just simply update the bgbsVolumeLabel but also need to create a volume lable file in root directory. The volume lable file is not a real file but just a file entry in root directory with zero file lenth and a very special file attribute, ATTR_VOLUME_ID. (defined in public\common\oak\drivers\fsd\fatutil\MAIN\fatutilp.h) Locating and accessing bootsector is quite straight forward, as long as we know the starting sector of a FAT volume, that's it. But where is the root directory? The layout of a typical FAT is like this Boot sector (Volume ID in the figure) followed by Reserved Sectors (1 on FAT12/16 and 32 on FAT32), then FAT chain table(s) (can be 1 or 2), after that is the root directory (FAT12/16 and not shows in the figure) then begining of the File and Directories. In FAT12/16, the root directory is placed right after FAT so it is not hard to caculate the offset in the volume. But in FAT32, this rule is no longer true: the first cluster of the root directory is determined by BGBPB_RootDirStrtClus (or offset 44 in boot sector). Although this field is usually 0x00000002 (it is how CE initial the root directory after formating a volume. Note we should never assume it is always true) which means the first cluster contains data but not like the root directory is contiguous in FAT12/16, it is just like a regular file can be fragmented. So we need to access the root directory (of FAT32) hopping one cluster to another by traversing FAT table. Let's trace the code now. Although the source of FAT driver is not available in CE Shared Source program, but the formatter, Fatutil.dll, is available in public\common\oak\drivers\fsd\fatutil\MAIN\formatdisk.cpp. Be aware the public code only provides formatter for FAT12/16/32 for ExFAT it is still not available. FormatVolumeInternal is the main worker function. With the knowledge here, you should be able the trace the code easily. But I would like to discuss the following code pieces     dwReservedSectors = (fo.dwFatVersion == 32) ? 32 : 1;     dwRootEntries = (fo.dwFatVersion == 32) ? 0 : fo.dwRootEntries; Note the dwReservedSectors is 32 in FAT32 and 1 in FAT12/16. Root Entries is another different mentioned in previous paragraph, 0 for FAT32 (dynamic allocated) and fixed size (usually 512, defined in DEFAULT_ROOT_ENTRIES in public\common\sdk\inc\fatutil.h) And then here   memset(pBootSec->bsVolumeLabel, 0x20, sizeof(pBootSec->bsVolumeLabel)); It sets the Volume Label as empty string. Now let's carry on to the next section - write the root directory.     if (fo.dwFatVersion == 32) {         if (!(fo.dwFlags & FATUTIL_FORMAT_TFAT)) {             dwRootSectors = dwSectorsPerCluster;         }         else {             DIRENTRY    dirEntry;             DWORD       offset;             int               iVolumeNo;             memset(pbBlock, 0, pdi->di_bytes_per_sect);             memset(&dirEntry, 0, sizeof(DIRENTRY));                         dirEntry.de_attr = ATTR_VOLUME_ID;             // the first one is volume label             memcpy(dirEntry.de_name, "TFAT       ", sizeof (dirEntry.de_name));             memcpy(pbBlock, &dirEntry, sizeof(dirEntry));              ...             // Skip the next step of zeroing out clusters             dwCurrentSec += dwSectorsPerCluster;             dwRootSectors = 0;         }     }     // Each new root directory sector needs to be zeroed.     memset(pbBlock, 0, cbSizeBlk);     iRootSec=0;     while ( iRootSec < dwRootSectors) { Basically, the code zero out the each entry in root directory depends on dwRootSectors. In FAT12/16, the dwRootSectors is calculated as the sectors we need for the root entries (512 for most of the case) and in FAT32 it just zero out the one cluster. Please note that, if it is a TFAT volume, it initialize the root directory with special volume label entries for some special purpose. Despite to its unusual initialization process for TFAT, it does provide a example for how to create a volume entry. With some minor modification, we can assign the volume label in FAT formatter and also remember to sync the volume label with bsVolumeLabel or bgbsVolumeLabel in boot sector.

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  • Management and Monitoring Tools for Windows Azure

    - by BuckWoody
    With such a large platform, Windows Azure has a lot of moving parts. We’ve done our best to keep the interface as simple as possible, while giving you the most control and visibility we can. However, as with most Microsoft products, there are multiple ways to do something – and I’ve always found that to be a good strength. Depending on the situation, I might want a graphical interface, a command-line interface, or just an API so I can incorporate the management into my own tools, or have third-party companies write other tools. While by no means exhaustive, I thought I might put together a quick list of a few tools you can use to manage and monitor Windows Azure components, from our IaaS, SaaS and PaaS offerings. Some of the products focus on one area more than another, but all are available today. I’ll try and maintain this list to keep it current, but make sure you check the date of this post’s update – if it’s more than six months old, it’s most likely out of date. Things move fast in the cloud. The Windows Azure Management Portal The primary tool for managing Windows Azure is our portal – most everything you need is there, from creating new services to querying a database. There are two versions as of this writing – a Silverlight client version, and a newer HTML5 version. The latter is being updated constantly to be in parity with the Silverlight client. There’s a balance in this portal between simplicity and power – we’re following the “less is more” approach, with increasing levels of detail as you work through the portal rather than overwhelming you with a single, long “more is more” page. You can find the Portal here: http://windowsazure.com (then click “Log In” and then “Portal”) Windows Azure Management API You can also use programming tools to either write your own interface, or simply provide management functions directly within your solution. You have two options – you can use the more universal REST API’s, which area bit more complex but work with any system that can write to them, or the more approachable .NET API calls in code. You can find the reference for the API’s here: http://msdn.microsoft.com/en-us/library/windowsazure/ee460799.aspx  All Class Libraries, for each part of Windows Azure: http://msdn.microsoft.com/en-us/library/ee393295.aspx  PowerShell Command-lets PowerShell is one of the most powerful scripting languages I’ve used with Windows – and it’s baked into all of our products. When you need to work with multiple servers, scripting is really the only way to go, and the Windows Azure PowerShell Command-Lets allow you to work across most any part of the platform – and can even be used within the services themselves. You can do everything with them from creating a new IaaS, PaaS or SaaS service, to controlling them and even working with security and more. You can find more about the Command-Lets here: http://wappowershell.codeplex.com/documentation (older link, still works, will point you to the new ones as well) We have command-line utilities for other operating systems as well: https://www.windowsazure.com/en-us/manage/downloads/  Video walkthrough of using the Command-Lets: http://channel9.msdn.com/Events/BUILD/BUILD2011/SAC-859T  System Center System Center is actually a suite of graphical tools you can use to manage, deploy, control, monitor and tune software from Microsoft and even other platforms. This will be the primary tool we’ll recommend for managing a hybrid or contiguous management process – and as time goes on you’ll see more and more features put into System Center for the entire Windows Azure suite of products. You can find the Management Pack and README for it here: http://www.microsoft.com/en-us/download/details.aspx?id=11324  SQL Server Management Studio / Data Tools / Visual Studio SQL Server has two built-in management and development, and since Version 2008 R2, you can use them to manage Windows Azure Databases. Visual Studio also lets you connect to and manage portions of Windows Azure as well as Windows Azure Databases. You can read more about Visual Studio here: http://msdn.microsoft.com/en-us/library/windowsazure/ee405484  You can read more about the SQL tools here: http://msdn.microsoft.com/en-us/library/windowsazure/ee621784.aspx  Vendor-Provided Tools Microsoft does not suggest or endorse a specific third-party product. We do, however, use them, and see lots of other customers use them. You can browse to these sites to learn more, and chat with their folks directly on how they support Windows Azure. Cerebrata: Tools for managing from the command-line, graphical diagnostics, graphical storage management - http://www.cerebrata.com/  Quest Cloud Tools: Monitoring, Storage Management, and costing tools - http://communities.quest.com/community/cloud-tools  Paraleap: Monitoring tool - http://www.paraleap.com/AzureWatch  Cloudgraphs: Monitoring too -  http://www.cloudgraphs.com/  Opstera: Monitoring for Windows Azure and a Scale-out pattern manager - http://www.opstera.com/products/Azureops/  Compuware: SaaS performance monitoring, load testing -  http://www.compuware.com/application-performance-management/gomez-apm-products.html  SOASTA: Penetration and Security Testing - http://www.soasta.com/cloudtest/enterprise/  LoadStorm: Load-testing tool - http://loadstorm.com/windows-azure  Open-Source Tools This is probably the most specific set of tools, and the list I’ll have to maintain most often. Smaller projects have a way of coming and going, so I’ll try and make sure this list is current. Windows Azure MMC: (I actually use this one a lot) http://wapmmc.codeplex.com/  Windows Azure Diagnostics Monitor: http://archive.msdn.microsoft.com/wazdmon  Azure Application Monitor: http://azuremonitor.codeplex.com/  Azure Web Log: http://www.xentrik.net/software/azure_web_log.html  Cloud Ninja:Multi-Tennant billing and performance monitor -  http://cnmb.codeplex.com/  Cloud Samurai: Multi-Tennant Management- http://cloudsamurai.codeplex.com/    If you have additions to this list, please post them as a comment and I’ll research and then add them. Thanks!

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  • Bubble shooter search alghoritm

    - by Fofole
    So I have a Matrix of NxM. At a given position (for ex. [2][5]) I have a value which represents a color. If there is nothing at that point the value is -1. What I need to do is after I add a new point, to check all his neighbours with the same color value and if there are more than 2, set them all to -1. If what I said doesn't make sense what I'm trying to do is an alghoritm which I use to destroy all the same color bubbles from my screen, where the bubbles are memorized in a matrix where -1 means no bubble and {0,1,2,...} represent that there is a bubble with a specific color. This is what I tried and failed: public class Testing { static private int[][] gameMatrix= {{3, 3, 4, 1, 1, 2, 2, 2, 0, 0}, {1, 4, 1, 4, 2, 2, 1, 3, 0, 0}, {2, 2, 4, 4, 3, 1, 2, 4, 0, 0}, {0, 1, 2, 3, 4, 1, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, }; static int Rows=6; static int Cols=10; static int count; static boolean[][] visited=new boolean[15][15]; static int NOCOLOR = -1; static int color = 1; public static void dfs(int r, int c, int color, boolean set) { for(int dr = -1; dr <= 1; dr++) for(int dc = -1; dc <= 1; dc++) if(!(dr == 0 && dc == 0) && ok(r+dr, c+dc)) { int nr = r+dr; int nc = c+dc; // if it is the same color and we haven't visited this location before if(gameMatrix[nr][nc] == color && !visited[nr][nc]) { visited[nr][nc] = true; count++; dfs(nr, nc, color, set); if(set) { gameMatrix[nr][nc] = NOCOLOR; } } } } static boolean ok(int r, int c) { return r >= 0 && r < Rows && c >= 0 && c < Cols; } static void showMatrix(){ for(int i = 0; i < gameMatrix.length; i++) { System.out.print("["); for(int j = 0; j < gameMatrix[0].length; j++) { System.out.print(" " + gameMatrix[i][j]); } System.out.println(" ]"); } System.out.println(); } static void putValue(int value,int row,int col){ gameMatrix[row][col]=value; } public static void main(String[] args){ System.out.println("Initial Matrix:"); putValue(1, 4, 1); putValue(1, 5, 1); showMatrix(); for(int n = 0; n < 15; n++) for(int m = 0; m < 15; m++) visited[n][m] = false; //reset count count = 0; //dfs(bubbles.get(i).getRow(), bubbles.get(i).getCol(), color, false); // get the contiguous count dfs(5,1,color,false); //if there are more than 2 set the color to NOCOLOR for(int n = 0; n < 15; n++) for(int m = 0; m < 15; m++) visited[n][m] = false; if(count > 2) { //dfs(bubbles.get(i).getRow(), bubbles.get(i).getCol(), color, true); dfs(5,1,color,true); } System.out.println("Matrix after dfs:"); showMatrix(); } }

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  • Estimating the boundary of arbitrarily distributed data

    - by Dave
    I have two dimensional discrete spatial data. I would like to make an approximation of the spatial boundaries of this data so that I can produce a plot with another dataset on top of it. Ideally, this would be an ordered set of (x,y) points that matplotlib can plot with the plt.Polygon() patch. My initial attempt is very inelegant: I place a fine grid over the data, and where data is found in a cell, a square matplotlib patch is created of that cell. The resolution of the boundary thus depends on the sampling frequency of the grid. Here is an example, where the grey region are the cells containing data, black where no data exists. OK, problem solved - why am I still here? Well.... I'd like a more "elegant" solution, or at least one that is faster (ie. I don't want to get on with "real" work, I'd like to have some fun with this!). The best way I can think of is a ray-tracing approach - eg: from xmin to xmax, at y=ymin, check if data boundary crossed in intervals dx y=ymin+dy, do 1 do 1-2, but now sample in y An alternative is defining a centre, and sampling in r-theta space - ie radial spokes in dtheta increments. Both would produce a set of (x,y) points, but then how do I order/link neighbouring points them to create the boundary? A nearest neighbour approach is not appropriate as, for example (to borrow from Geography), an isthmus (think of Panama connecting N&S America) could then close off and isolate regions. This also might not deal very well with the holes seen in the data, which I would like to represent as a different plt.Polygon. The solution perhaps comes from solving an area maximisation problem. For a set of points defining the data limits, what is the maximum contiguous area contained within those points To form the enclosed area, what are the neighbouring points for the nth point? How will the holes be treated in this scheme - is this erring into topology now? Apologies, much of this is me thinking out loud. I'd be grateful for some hints, suggestions or solutions. I suspect this is an oft-studied problem with many solution techniques, but I'm looking for something simple to code and quick to run... I guess everyone is, really! Cheers, David

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  • Embedded "Smart" character LCD driver. Is this a good idea?

    - by chris12892
    I have an embedded project that I am working on, and I am currently coding the character LCD driver. At the moment, the LCD driver only supports "dumb" writing. For example, let's say line 1 has some text on it, and I make a call to the function that writes to the line. The function will simply seek to the beginning of the line and write the text (plus enough whitespace to erase whatever was last written). This is well and good, but I get the feeling it is horribly inefficient sometimes, since some lines are simply: "Some-reading: some-Value" Rather than "brute force" replacing the entire line, I wanted to develop some code that would figure out the best way to update the information on the LCD. (just as background, it takes 2 bytes to seek to any char position. I can then begin writing the string) My idea was to first have a loop. This loop would compare the input to the last write, and in doing so, it would cover two things: A: Collect all the differences between the last write and the input. For every contiguous segment (be it same or different) add two bytes to the byte count. This is referenced in B to determine if we are wasting serial bandwidth. B: The loop would determine if this is really a smart thing to do. If we end up using more bytes to update the line than to "brute force" the line, then we should just return and let the brute force method take over. We should exit the smart write function as soon as this condition is met to avoid wasting time. The next part of the function would take all the differences, seek to the required char on the LCD, and write them. Thus, if we have a string like this already on the LCD: "Current Temp: 80F" and we want to update it to "Current Temp: 79F" The function will go through and see that it would take less bandwidth to simply seek to the "8" and write "79". The "7" will cover the "8" and the "9" will cover the "0". That way, we don't waste time writing out the entire string. Does this seem like a practical idea?

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  • What the best approach to iterate and "store" files over a directory in C (Linux) ?

    - by Andrei Ciobanu
    I have written a function that checks if to files are duplicates or not. This function signature is: int check_dup_memmap(char *f1_name, char *f2_name) It returns: (-1) - If something went wrong; (0) - If the two files are similar; (+1) - If the two files are different; The next step is to write a function that iterates through all the files in a certain directory,apply the previous function, and gives a report on every existing duplicates. Initially I've thought to write a function that generates a file with all the filenames in a certain directory and then, read that file again and gain and compare every two files. Here is that version of the function, that gets all the filenames in a certain directory. void *build_dir_tree(char *dirname, FILE *f) { DIR *cdir = NULL; struct dirent *ent = NULL; struct stat buf; if(f == NULL){ fprintf(stderr, "NULL file submitted. [build_dir_tree].\n"); exit(-1); } if(dirname == NULL){ fprintf(stderr, "NULL dirname submitted. [build_dir_tree].\n"); exit(-1); } if((cdir = opendir(dirname)) == NULL){ char emsg[MFILE_LEN]; sprintf(emsg, "Cannot open dir: %s [build_dir_tree]\t",dirname); perror(emsg); } chdir(dirname); while ((ent = readdir(cdir)) != NULL) { lstat(ent->d_name, &buf); if (S_ISDIR(buf.st_mode)) { if (strcmp(".", ent->d_name) == 0 || strcmp("..", ent->d_name) == 0) { continue; } build_dir_tree(ent->d_name, f); } else{ fprintf(f, "/%s/%s\n",util_get_cwd(),ent->d_name); } } chdir(".."); closedir(cdir); } Still I consider this approach a little inefficient, as I have to parse the file again and again. In your opinion what are other approaches should I follow: Write a datastructure and hold the files instead of writing them in the file ? I think for a directory with a lot of files, the memory will become very fragmented. Hold all the filenames in auto-expanding array, so that I can easy access every file by their index, because they will in a contiguous memory location. Map this file in memory using mmap() ? But mmap may fail, as the file gets to big. Any opinions on this. I want to choose the most efficient path, and access as few resources as possible. This is the requirement of the program... EDIT: Is there a way to get the numbers of files in a certain directory, without iterating through it ?

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  • e2fsck / resize2fs problems

    - by BlakBat
    I've got 6 drives (each 1.5T, all same model and firmware revision) that are part of a RAID5 array. The RAID5 makes a LVM volume group and a logical group. The latter contains only one ext3 partition. I've recently ran: e2fsck -f /dev/vg03/lv01 && resize2fs -M /dev/vg03/lv01 which exited without an error. Now when I try to mount /dev/vg03/lv01 I get: EXT3-fs error (device dm-0): ext3_check_descriptors: Block bitmap for group 30533 not in group (block 1000532368)! EXT3-fs: group descriptors corrupted! How do I get out of this predicament? This is all the info I can currently give you: fdisk -l /dev/sd[cdefgh] shows (correctly) that they are "Linux raid autodetect" but fdisk now shows: fdisk -l /dev/md0 Disk /dev/md0: 7501.5 GB, 7501495664640 bytes ... Disk identifier: 0x00000000 Disk /dev/md0 doesn't contain a valid partition table (instead of a LVM type partition) fdisk -l /dev/vg03/lv01 Disk /dev/vg03/lv01: 7501.5 GB, 7501491732480 bytes ... Disk identifier: 0x00000000 Disk /dev/vg03/lv01 doesn't contain a valid partition table (instead of a ext3 type partition) I've tried: e2fsck -fy /dev/vg03/lv01 e2fsck 1.41.12 (17-May-2010) e2fsck: Group descriptors look bad... trying backup blocks... Block bitmap for group 30533 is not in group. (block 1000532368) Relocate? yes Inode bitmap for group 30533 is not in group. (block 1000532369) Relocate? yes Pass 1: Checking inodes, blocks, and sizes Relocating group 30533's block bitmap to 1000524246... Error allocating 1 contiguous block(s) in block group 30533 for inode bitmap: Could not allocate block in ext2 filesystem e2fsck: aborted Extra information I can give you: cat /proc/mdstat Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active (auto-read-only) raid5 sdg1[0] sdh1[5] sdf1[4] sde1[3] sdc1[2] sdd1[1] 7325679360 blocks level 5, 128k chunk, algorithm 2 [6/6] [UUUUUU] bitmap: 1/175 pages [4KB], 4096KB chunk unused devices: Lastly, all smartctl tests (short and extendend) showed no errors on any of the disks. Should I try to resize2fs to grow /dev/vg03/lv01 and redo a e2fsck ? Should I cfdisk /dev/md0 and /dev/vg03/lv01 back to their real types? Thanks in advance for all and any help. 2011-09-20 UPDATE I issued the following commands and was able to remount the partition, but by viewing the size (df) of before and after, it seems that 1Tb of data have gone missing. By checking the MD5SUMS (from an old backup) of some files with the "same" files from the remounted partition, some errors have been detected. Commands issued to remount the partition were: dumpe2fs /dev/vg03/lv01 Block count: 1000491435<br /> Block size: 4096<br /> tune2fs -O ^has_journal /dev/vg03/lv01 resize2fs -p /dev/vg03/lv01 dumpe2fs /dev/vg03/lv01 Block count: 1831418880<br /> Block size: 4096<br /> mount -o ro,noatime /dev/vg03/lv01 /mnt/raid OK... but files have been damaged / gone missing.

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