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  • Disable writing RAID degraded mode

    - by jolivier
    I have a RAID5 with 5 disks on my machine and suspect the motherboard chipset to fail at some points and make my raid going in degraded mode. Last time it happened I noticed it on the failure of the 2nd drive connected to the same chipset and lost a lot of data. So I would like to prevent this, and especially I would like to have mdadm disable writes on the raid if one of the disk fails. So that in between I get notified, I recover and can use my system again. Sadly I could not find it in man mdadm so I was wondering if this is possible via a tool or hidden option since for me it looks like a standard feature of a RAID system. If this is not possible I would also be happy with a solution to stop the raid if degraded.

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  • Is there a way to create a copy-on-write copy of a directory?

    - by BCS
    I'm thinking of a situation where I would have something that creates a copy of a directory, tweaks a few files, and then does some processing on the result. This wold be done fairly often, maybe a few dozen times a day. (The exact use case is testing patch submissions; dupe the code, patch it, build/test/report/etc.) What I'm looking for could be done by creating a new directory structure and populating it with hard links from the origonal. However this only works if all the tools you use delete and recreate files rather than edit them in place. Is there a way to have the file system do copy-on-write for a file? Note: I'm aware that many FSs use COW at a block level (all updates are done via writes to new blocks) but this is not what I want.

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  • Mimicking Google's Persistant Disks -- Is this a logical FreeBSD disaster recovery strategy?

    - by Casey Jordan
    I am looking into FreeBSD to provide a more comprehensive backup and disaster recovery strategy for database servers. Ideally I want to mimic what google is doing with "Persistant disks" https://developers.google.com/compute/docs/disks#snapshots I am hoping someone who knows more about FreeBSD can validate these ideas/questions: I have read that FreeBSD can take instant disk snapshots, therefore if our databases trigger a consistent state (Block all writes, and flush buffers to disk), I would assume I could take snapshots every hour without service interruption for more than a few seconds. Is this true? Is there a way to take snapshots and back them up offsite easily? Can this be done incrementally as to save how much disk space is actually used? If a rollback needed to be done, how long does this typically take? Is a rollback also instantaneous? Thanks!

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  • Kill child process when the parent exits

    - by kolypto
    I'm preparing a script for Docker, which allows only one top-level process, which should receive the signals so we can stop it. Therefore, I'm having a script like this: one application writes to syslog (bash script in this sample), and the other one just prints it. #! /usr/bin/env bash set -eu tail -f /var/log/syslog & exec bash -c 'while true ; do logger aaaaaaaaaaaaaaaaaaa ; sleep 1 ; done' Almost solved: when the top-level process bash gets SIGTERM -- it exists, but tail -f continues to run. How do I instruct tail -f to exit when the parent process exits? E.g. it should also get the signal. Note: Can't use bash traps since exec on the last line replaces the process completely.

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  • Access denied to EFS encrypted files after PC joins domain

    - by mjmarsh
    I'm experiencing strange behavior with Windows Encrypted File System: I have a machine that is in workgroup mode (not joined to a domain) I encrypt an entire directory structure on the machine (basically a folder and subfolders with data files for my application). My application writes and reads files from the encrypted file hierarchy as a local Windows user (let's call the account 'SecureUser'). This works fine I then join the PC to a domain (Let's call it 'TEST') Afterwards, processes running as the local 'SecureUser' account can't read the files it wrote originally when it was off the domain (What is also strange is that the files are listed as "read only" now and I cannot unset this flag via Windows Explorer or the command line, even though it looks like it succeeds) I then 'un-join' the PC from the domain and everything works again Is there something about changing domain membership on a PC that changes the behavior of EFS so that previously encrypted files cannot be read, even by the originating user? Thanks in advance

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  • What needs updating when moving a bootable Windows 7 (or Vista) partition?

    - by SuperTempel
    When I move a bootable NTFS partition with Windows on it to a different block offset, what needs updating to make it bootable again? In particular, here's what I tried: I have a disk with several partitions, one of which is the NTFS partition with Windows on it, and the disk uses the plain old MBR block 0 for the partitions layout (no more than 4 partitions). Now I format and partition a new, larger, disk. There I make room for the NTFS partition and copy the contents from the old disk's NTFS Windows partition into. And I make the partition "active". However, when I try to boot from this disk, I get a "read error" message immediately and the booting stops, the exact text is: A disk read error occurred Press Ctrl+Alt+Del to restart I verified that both disks have the same boot sector code in block 0. It seems to me that something else might need updating. I guess that somewhere there's a absolute block reference that I need to update, probably pointing to the next level loader or to the NT kernel. Update: I found this article going quite into the depth of what I want to know. However, it says to modify boot.ini, but I have Windows 7 installed here, where such things appear to have changed: No boot.ini but a folder called System Volume Information with GUID and other data in it that sounds related to my problem. Going to keep digging... Update 2: Thanks to the terrible looking but very informative website by starman, I was able to figure out the first step: The NTFS boot sector has a field for "hidden" sectors. This feld has to contain the sector number of the boot sector. This solves the "read error" message. Now, however, I get a "BOOTMGR is missing" error instead. Looks like there's another place where a block number has to be adjusted, but I can't find anything in the code listing about this. I do find a lot of help sites suggesting Windows tools for fixing this "BOOTMGR is missing" problem, but none seem to know what goes on behind the scenes. Kind of like suggesting to re-install Windows when there's a little problem with it. At least, those fixes seem to work, mostly involving the Bcdedit and Bootrec tools. Now, who knows what they do, especially the latter, in regards to a moved partition? Update 3: After lots of trial-and-error attempts, I believe now that the solution lies in the BCD-Template registry file, residing usually inside \Windows\System32\config. If I get this updated using the "bcdboot" command, Windows starts up from it. I am now in the middle of figuring out what information this registry contains relevant to the above question. Any pointers to the contents of this registry are welcome. Update 4: Turns out that while the BCD-Template file gets rewritten and has different binary contents than its predecessor, the values inside do not change. So it must be something else that bcdboot.exe writes. I had previously already checked if it changes the first 32 boot blocks of the partition, but they appear to remain unchanged. Parititon map doesn't get changed, either. So what is it that bcdboot modifies besides the BCD registry? Any tips on how I can trace that? Are there low level tools that show me what files a program writes to? Update 5: The answer seems to be: c:\Boot\BCD is also changed, and that appears to be the key file for the boot manager's process. I'll investigate this later... Update 6: It seems to be an important detail that I had originally two partitions created when I installed Windows 7: A small partition of 204800 sectors which appears to be a bootstrap partition, followed by the actual, large, partition containing the Windows system (drive C:). When I tried to transfer this installation to a new, larger, disk, I had kept the same two partitions intact on the new drive, although they ended up at a different offset. This alone led to the "BOOTMGR is missing" message. Since then, I've used bcdboot.exe only on the Windows partition, which added the \Boot\BCD file on that partition. That file (and folder) did originally only exist on the smaller partition. Hence, this problem may be more complicated in my case as one partition (the boot strapper) referred to another partition (the one containing the OS), whereas other people may only have to deal with one partition containing both, and maybe there the solution is simpler. Update 7: Found one more detail: The \Boot\BCD file records the MBR's serial number. If that number doesn't match, the system won't boot. Next I'll test if there's also an absolute block reference stored in there.

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  • Oracle backup and recovery

    - by kupa
    During recovery Oracle writes the following error: RMAN-06054: media recovery requesting unknown log: thread 1 seq 9 lowscn 4034762 I have used in mount mode this command: change archivelog all crosscheck; delete expired archivelog all; Then restore and tried to recover again:But still RMAN-06054 error.Than I wrote: run{ SET UNTIL SEQUENCE 9 THREAD 1; RESTORE DATABASE; RECOVER DATABASE; } It helped me to recover database...But after that when I do the backup and then recover the same error occurs and solution is the same... I wonder to solve this problem without SET UNTIL SEQUENCE 9 THREAD 1; maybe I should unregister this archive log from control file(I am using control file not catalog) Can you tell me how?

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  • Can an SSD notify the hosting OS that its wear level is getting high?

    - by Tony_Henrich
    I read a lot about SSDs and I am interested in them for server use. My biggest concern is their reliability. A lot of writes shortens their life span. I can mitigate this problem if I can run some kind of diagnostics on a regular basis on the SSD or if the SSD can automatically warn the OS that its reliability is reaching a critical level. Think of this as S.M.A.R.T or software like SpinRite for SSDs. Does anything I mentioned exist now? Which kind/brand of SSD does this? I don't mind swapping out a tired SSD for a newer one once a while. I am pretty sure that SSDs life is calculated in years and not in few months? For me, the improved performance will pay for the SSD over and over. I am planning to use plenty of RAM as well.

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  • What are the pros & cons of these MySQL engines for OLTP -- XtraDB, PBXT, or TokuDB?

    - by Continuation
    I'm working on a social website with an approximate read/write split of 90/10. Trying to decide on a MySQL engine. The ones I'm interested in are: XtraDB PBXT TokuDB What are the pros and cons of them for my use case? A few specific questions: PBXT uses log-based structure that avoids double-writes. It sounds very elegant, but the benchmark I've seen doesn't show any/much advantages over XtraDB. Do you have any experience with PBXT/XtraDB you can share? TokuDB sounds VERY interesting. But all the benchmarks I've seen are about single-threaded bulk inserts - inserting 100M rows for example. that's not very relevant for OLTP. What about its performance with large number of concurrent threads writing and reading at the same time? Anyone has tried that?

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  • How can I sync Access databases and keep them up-to-date?

    - by user327472
    I have an Access database on my server. We split it up and use the front-end database for search data and adding new records or reports in local computer. If we update or add a new record, that writes to the back-end of database. I want to use this database in the other building with other servers. Also, those servers have no direct connection. How can I sync both back-end databases to keep the database data up to date? These details may be useful: It's a big amount of data - about 25,750 client records. I guess there are more than 25 tables at 80 MB.

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  • Will readyboost speed up a secondary partion or harddrive?

    - by Sebastian
    I'm building a new computer and plan on using a few spare USB sticks with readyboost to cache disk writes. I'll be running Windows 7 Enterprise SP1 x64 I have a single 2 TB disk, and plan to make a partition for windows (100 GB) and use the rest for data. I know Readyboost will work nicely for the C drive, but am unable to find any information on whether it will accelerate a second drive or partition. Just to clarify, I'm NOT trying to use the harddrive instead of the usb sticks. I'm trying to speed up the second partition using the USB sticks So, will readyboost work for a secondary partion or harddrive?

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  • Is there good FAT driver for FUSE? (Lightweight, not mountlo)

    - by Vi.
    FUSE filesystem list show some FuseFat and FatFuse. Both are old, FatFuse is read-only , FuseFat is non-buildable and probably depends on glib. Now I'm using mountlo for the task (mounting USB drives in generic way without root access or suid things (except of fusermount itself)), but it looks too big for such task. Using FUSE to mount external storage devices is good both for security and for flexibility reason: the kernel sees only block reads and writes while actual code that deals with filesystem details runs with user privileges, allowing user to use custom filesystems and preventing from kernel filesystem exploits. Is there good vfat FUSE driver?

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  • What is and what is not replicated in a glassfish cluster with a mod_jk load balancer?

    - by Navigateur
    I have a Glassfish (3.1.2) cluster over 2 computers as nodes, with a mod_jk load balancer. Are servlet instance variables replicated perfectly? If not, how do I make sure it is? Are all actions, including method calls and disk writes, replicated perfectly? If not, how do I make sure they are? These may seem like stupid questions, but I'm not seeking "load balancing" as much as I am seeking exact replication to enable future upgrading without any service interruption. How do I achieve this if it is not already the case?

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  • Large recovery partitions

    - by Unsigned
    Is there any good reason as to why factory restore partitions are generally much larger than they need to be? Examples I have found in my own experience: Dell XPS laptop Partition: 13.67 GB Used: 6.68 GB Dell Inspiron laptop Partition: 14.7 GB Used: 7.2 GB Toshiba laptop Partition: 15.3 GB Used: 9 GB In all cases, shrinking the partition to only slightly more than the Used space had no ill effects on future factory restorations. Why the exorbitant amount of extra space, given that neither of the three computers ever writes any data to the recovery partition? Is there a good reason I'm overlooking?

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  • Windows NT Service shutdown issues

    - by Jeremiah Gowdy
    I have developed middleware that provides RPC functionality to multiple client applications on multiple platforms within our organization. The middleware is written in C# and runs as a Windows NT Service. It handles things like file access to network shares, database access, etc. The middleware is hosted on two high end systems running Windows Server 2008 R2. When one of our server administrators goes to reboot the machine, primarily to do Windows Updates, there are serious problems with how the system behaves in regards to my NT Service. My service is designed to immediately stop listening for new connections, immediately start refusing new requests on existing connections, and otherwise shut down as rapidly as possible in the case of an OnStop or OnShutdown request from the SCM. Still, to maintain system integrity, operations that are currently in progress are allowed to continue for a reasonable time. Usually the server shuts down inside of 30 seconds (when the service is manually stopped for example). However, when the system is instructed to restart, my service immediately loses access to network drives and UNC paths, causing data integrity problems for any open files and partial writes to those locations. My service does list Workstation (and thus SMB Redirector) as a dependency, so I would think that my service would need to be stopped prior to Workstation/Redirector being stopped if Windows were honoring those dependencies. Basically, my application is forced to crash and burn, failing remote procedure calls and eventually being forced to terminate by the operating system after a timeout period has elapsed (seems to be on the order of 20-30 seconds). Unlike a Windows application, my Windows NT Service doesn't seem to have any power to stop a system shutdown in progress, delay the system shutdown, or even just the opportunity to save out any pending network share disk writes before being forcibly disconnected and shutdown. How is an NT Service developer supposed to have any kind of application integrity in this environment? Why is it that Forms Applications get all of the opportunity to finish their business prior to shutdown, while services seem to get no such benefits? I have tried: Calling SetProcessShutdownParameters via p/invoke to try to notify my application of the shutdown sooner to avoid Redirector shutting down before I do. Calling ServiceBase.RequestAdditionalTime with a value less than or equal to the two minute limit. Tweaking the WaitToKillServiceTimeout Everything I can think of to make my service shutdown faster. But in the end, I still get ~30 seconds of problematic time in which my service doesn't even seem to have been notified of an OnShutdown event yet, but requests are failing due to redirector no longer servicing my network share requests. How is this issue meant to be resolved? What can I do to delay or stop the shutdown, or at least be allowed to shut down my active tasks without Redirector services disappearing out from under me? I can understand what Microsoft is trying to do to prevent services from dragging their feet and showing shutdowns, but that seems like a great goal for Windows client operating systems, not for servers. I don't want my servers to shutdown fast, I want operational integrity and graceful shutdowns. Thanks in advance for any help you can provide. PS in regards to writing my own middleware, this is for a telephony application with sub-second "soft-realtime" response time requirements. It does make sense, and it's not a point I'm looking to debate. :)

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  • Why can't Java servlet sent out an object ?

    - by Frank
    I use the following method to send out an object from a servlet : public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException { String Full_URL=request.getRequestURL().append("?"+request.getQueryString()).toString(); String Contact_Id=request.getParameter("Contact_Id"); String Time_Stamp=Get_Date_Format(6),query="select from "+Contact_Info_Entry.class.getName()+" where Contact_Id == '"+Contact_Id+"' order by Contact_Id desc"; PersistenceManager pm=null; try { pm=PMF.get().getPersistenceManager(); // note that this returns a list, there could be multiple, DataStore does not ensure uniqueness for non-primary key fields List<Contact_Info_Entry> results=(List<Contact_Info_Entry>)pm.newQuery(query).execute(); Write_Serialized_XML(response.getOutputStream(),results.get(0)); } catch (Exception e) { Send_Email(Email_From,Email_To,"Check_License_Servlet Error [ "+Time_Stamp+" ]",new Text(e.toString()+"\n"+Get_Stack_Trace(e)),null); } finally { pm.close(); } } /** Writes the object and CLOSES the stream. Uses the persistance delegate registered in this class. * @param os The stream to write to. * @param o The object to be serialized. */ public static void writeXMLObject(OutputStream os,Object o) { // Classloader reference must be set since netBeans uses another class loader to loead the bean wich will fail in some circumstances. ClassLoader oldClassLoader=Thread.currentThread().getContextClassLoader(); Thread.currentThread().setContextClassLoader(Check_License_Servlet.class.getClassLoader()); XMLEncoder encoder=new XMLEncoder(os); encoder.setExceptionListener(new ExceptionListener() { public void exceptionThrown(Exception e) { e.printStackTrace(); }}); encoder.writeObject(o); encoder.flush(); encoder.close(); Thread.currentThread().setContextClassLoader(oldClassLoader); } private static ByteArrayOutputStream writeOutputStream=new ByteArrayOutputStream(16384); /** Writes an object to XML. * @param out The boject out to write to. [ Will not be closed. ] * @param o The object to write. */ public static synchronized void writeAsXML(ObjectOutput out,Object o) throws IOException { writeOutputStream.reset(); writeXMLObject(writeOutputStream,o); byte[] Bt_1=writeOutputStream.toByteArray(); byte[] Bt_2=new Des_Encrypter().encrypt(Bt_1,Key); out.writeInt(Bt_2.length); out.write(Bt_2); out.flush(); out.close(); } public static synchronized void Write_Serialized_XML(OutputStream Output_Stream,Object o) throws IOException { writeAsXML(new ObjectOutputStream(Output_Stream),o); } At the receiving end the code look like this : File_Url="http://"+Site_Url+App_Dir+File_Name; try { Contact_Info_Entry Online_Contact_Entry=(Contact_Info_Entry)Read_Serialized_XML(new URL(File_Url)); } catch (Exception e) { e.printStackTrace(); } private static byte[] readBuf=new byte[16384]; public static synchronized Object readAsXML(ObjectInput in) throws IOException { // Classloader reference must be set since netBeans uses another class loader to load the bean which will fail under some circumstances. ClassLoader oldClassLoader=Thread.currentThread().getContextClassLoader(); Thread.currentThread().setContextClassLoader(Tool_Lib_Simple.class.getClassLoader()); int length=in.readInt(); readBuf=new byte[length]; in.readFully(readBuf,0,length); byte Bt[]=new Des_Encrypter().decrypt(readBuf,Key); XMLDecoder dec=new XMLDecoder(new ByteArrayInputStream(Bt,0,Bt.length)); Object o=dec.readObject(); Thread.currentThread().setContextClassLoader(oldClassLoader); in.close(); return o; } public static synchronized Object Read_Serialized_XML(URL File_Url) throws IOException { return readAsXML(new ObjectInputStream(File_Url.openStream())); } But I can't get the object from the Java app that's on the receiving end, why ? The error messages look like this : java.lang.ClassNotFoundException: PayPal_Monitor.Contact_Info_Entry Continuing ... java.lang.NullPointerException: target should not be null Continuing ... java.lang.NullPointerException: target should not be null Continuing ... java.lang.NullPointerException: target should not be null Continuing ...

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  • Forcing a transaction to rollback on validation errors in Seam

    - by Chris Williams
    Quick version: We're looking for a way to force a transaction to rollback when specific situations occur during the execution of a method on a backing bean but we'd like the rollback to happen without having to show the user a generic 500 error page. Instead, we'd like the user to see the form she just submitted and a FacesMessage that indicates what the problem was. Long version: We've got a few backing beans that use components to perform a few related operations in the database (using JPA/Hibernate). During the process, an error can occur after some of the database operations have happened. This could be for a few different reasons but for this question, let's assume there's been a validation error that is detected after some DB writes have happened that weren't detectible before the writes occurred. When this happens, we'd like to make sure all of the db changes up to this point will be rolled back. Seam can deal with this because if you throw a RuntimeException out of the current FacesRequest, Seam will rollback the current transaction. The problem with this is that the user is shown a generic error page. In our case, we'd actually like the user to be shown the page she was on with a descriptive message about what went wrong, and have the opportunity to correct the bad input that caused the problem. The solution we've come up with is to throw an Exception from the component that discovers the validation problem with the annotation: @ApplicationException( rollback = true ) Then our backing bean can catch this exception, assume the component that threw it has published the appropriate FacesMessage, and simply return null to take the user back to the input page with the error displayed. The ApplicationException annotation tells Seam to rollback the transaction and we're not showing the user a generic error page. This worked well for the first place we used it that happened to only be doing inserts. The second place we tried to use it, we have to delete something during the process. In this second case, everything works if there's no validation error. If a validation error does happen, the rollback Exception is thrown and the transaction is marked for rollback. Even if no database modifications have happened to be rolled back, when the user fixes the bad data and re-submits the page, we're getting: java.lang.IllegalArgumentException: Removing a detached instance The detached instance is lazily loaded from another object (there's a many to one relationship). That parent object is loaded when the backing bean is instantiated. Because the transaction was rolled back after the validation error, the object is now detached. Our next step was to change this page from conversation scope to page scope. When we did this, Seam can't even render the page after the validation error because our page has to hit the DB to render and the transaction has been marked for rollback. So my question is: how are other people dealing with handling errors cleanly and properly managing transactions at the same time? Better yet, I'd love to be able to use everything we have now if someone can spot something I'm doing wrong that would be relatively easy to fix. I've read the Seam Framework article on Unified error page and exception handling but this is geared more towards more generic errors your application might encounter.

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  • Random Complete System Unresponsiveness Running Mathematical Functions

    - by Computer Guru
    I have a program that loads a file (anywhere from 10MB to 5GB) a chunk at a time (ReadFile), and for each chunk performs a set of mathematical operations (basically calculates the hash). After calculating the hash, it stores info about the chunk in an STL map (basically <chunkID, hash>) and then writes the chunk itself to another file (WriteFile). That's all it does. This program will cause certain PCs to choke and die. The mouse begins to stutter, the task manager takes 2 min to show, ctrl+alt+del is unresponsive, running programs are slow.... the works. I've done literally everything I can think of to optimize the program, and have triple-checked all objects. What I've done: Tried different (less intensive) hashing algorithms. Switched all allocations to nedmalloc instead of the default new operator Switched from stl::map to unordered_set, found the performance to still be abysmal, so I switched again to Google's dense_hash_map. Converted all objects to store pointers to objects instead of the objects themselves. Caching all Read and Write operations. Instead of reading a 16k chunk of the file and performing the math on it, I read 4MB into a buffer and read 16k chunks from there instead. Same for all write operations - they are coalesced into 4MB blocks before being written to disk. Run extensive profiling with Visual Studio 2010, AMD Code Analyst, and perfmon. Set the thread priority to THREAD_MODE_BACKGROUND_BEGIN Set the thread priority to THREAD_PRIORITY_IDLE Added a Sleep(100) call after every loop. Even after all this, the application still results in a system-wide hang on certain machines under certain circumstances. Perfmon and Process Explorer show minimal CPU usage (with the sleep), no constant reads/writes from disk, few hard pagefaults (and only ~30k pagefaults in the lifetime of the application on a 5GB input file), little virtual memory (never more than 150MB), no leaked handles, no memory leaks. The machines I've tested it on run Windows XP - Windows 7, x86 and x64 versions included. None have less than 2GB RAM, though the problem is always exacerbated under lower memory conditions. I'm at a loss as to what to do next. I don't know what's causing it - I'm torn between CPU or Memory as the culprit. CPU because without the sleep and under different thread priorities the system performances changes noticeably. Memory because there's a huge difference in how often the issue occurs when using unordered_set vs Google's dense_hash_map. What's really weird? Obviously, the NT kernel design is supposed to prevent this sort of behavior from ever occurring (a user-mode application driving the system to this sort of extreme poor performance!?)..... but when I compile the code and run it on OS X or Linux (it's fairly standard C++ throughout) it performs excellently even on poor machines with little RAM and weaker CPUs. What am I supposed to do next? How do I know what the hell it is that Windows is doing behind the scenes that's killing system performance, when all the indicators are that the application itself isn't doing anything extreme? Any advice would be most welcome.

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  • Break a class in twain, or impose an interface for restricted access?

    - by bedwyr
    What's the best way of partitioning a class when its functionality needs to be externally accessed in different ways by different classes? Hopefully the following example will make the question clear :) I have a Java class which accesses a single location in a directory allowing external classes to perform read/write operations to it. Read operations return usage stats on the directory (e.g. available disk space, number of writes, etc.); write operations, obviously, allow external classes to write data to the disk. These methods always work on the same location, and receive their configuration (e.g. which directory to use, min disk space, etc.) from an external source (passed to the constructor). This class looks something like this: public class DiskHandler { public DiskHandler(String dir, int minSpace) { ... } public void writeToDisk(String contents, String filename) { int space = getAvailableSpace(); ... } public void getAvailableSpace() { ... } } There's quite a bit more going on, but this will do to suffice. This class needs to be accessed differently by two external classes. One class needs access to the read operations; the other needs access to both read and write operations. public class DiskWriter { DiskHandler diskHandler; public DiskWriter() { diskHandler = new DiskHandler(...); } public void doSomething() { diskHandler.writeToDisk(...); } } public class DiskReader { DiskHandler diskHandler; public DiskReader() { diskHandler = new DiskHandler(...); } public void doSomething() { int space = diskHandler.getAvailableSpace(...); } } At this point, both classes share the same class, but the class which should only read has access to the write methods. Solution 1 I could break this class into two. One class would handle read operations, and the other would handle writes: // NEW "UTILITY" CLASSES public class WriterUtil { private ReaderUtil diskReader; public WriterUtil(String dir, int minSpace) { ... diskReader = new ReaderUtil(dir, minSpace); } public void writeToDisk(String contents, String filename) { int = diskReader.getAvailableSpace(); ... } } public class ReaderUtil { public ReaderUtil(String dir, int minSpace) { ... } public void getAvailableSpace() { ... } } // MODIFIED EXTERNALLY-ACCESSING CLASSES public class DiskWriter { WriterUtil diskWriter; public DiskWriter() { diskWriter = new WriterUtil(...); } public void doSomething() { diskWriter.writeToDisk(...); } } public class DiskReader { ReaderUtil diskReader; public DiskReader() { diskReader = new ReaderUtil(...); } public void doSomething() { int space = diskReader.getAvailableSpace(...); } } This solution prevents classes from having access to methods they should not, but it also breaks encapsulation. The original DiskHandler class was completely self-contained and only needed config parameters via a single constructor. By breaking apart the functionality into read/write classes, they both are concerned with the directory and both need to be instantiated with their respective values. In essence, I don't really care to duplicate the concerns. Solution 2 I could implement an interface which only provisions read operations, and use this when a class only needs access to those methods. The interface might look something like this: public interface Readable { int getAvailableSpace(); } The Reader class would instantiate the object like this: Readable diskReader; public DiskReader() { diskReader = new DiskHandler(...); } This solution seems brittle, and prone to confusion in the future. It doesn't guarantee developers will use the correct interface in the future. Any changes to the implementation of the DiskHandler could also need to update the interface as well as the accessing classes. I like it better than the previous solution, but not by much. Frankly, neither of these solutions seems perfect, but I'm not sure if one should be preferred over the other. I really don't want to break the original class up, but I also don't know if the interface buys me much in the long run. Are there other solutions I'm missing?

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  • Windows DD-esque implementation in Qt 5

    - by user1777667
    I'm trying to get into Qt and as a project I want to try and pull a binary image from a hard drive in Windows. This is what I have: QFile dsk("//./PhysicalDrive1"); dsk.open(QIODevice::ReadOnly); QByteArray readBytes = dsk.read(512); dsk.close(); QFile img("C:/out.bin"); img.open(QIODevice::WriteOnly); img.write(readBytes); img.close(); When I run it, it creates the file, but when I view it in a hex editor, it says: ëR.NTFS ..........ø..?.ÿ.€.......€.€.ÿç......UT..............ö.......ì§á.Íá.`....ú3ÀŽÐ¼.|ûhÀ...hf.ˈ...f.>..NTFSu.´A»ªUÍ.r..ûUªu.÷Á..u.éÝ..ƒì.h..´HŠ...‹ô..Í.ŸƒÄ.žX.rá;...uÛ£..Á.....Z3Û¹. +Èfÿ.......ŽÂÿ...èK.+Èwï¸.»Í.f#Àu-f.ûTCPAu$.ù..r..h.».hp..h..fSfSfU...h¸.fa..Í.3À¿(.¹Ø.üóªé_...f`..f¡..f.....fh....fP.Sh..h..´BŠ.....‹ôÍ.fY[ZfYfY..‚..fÿ.......ŽÂÿ...u¼..faàø.è.. û.è..ôëý´.‹ð¬<.t.´.»..Í.ëòÃ..A disk read error occurred...BOOTMGR is missing...BOOTMGR is compressed...Press Ctrl+Alt+Del to restart...Œ©¾Ö..Uª Is there a better way of doing this? I tried running it as admin, but still no dice. Any help would be much appreciated. Update: I changed the code a bit. Now if I specify a dd images as the input it writes the image perfectly, but when I try to use a disk as the input it only writes 0x00. QTextStream(stdout) << "Start\n"; QFile dsk("//./d:"); //QFile dsk("//./PhysicalDrive1"); //QFile dsk("//?/Device/Harddisk1/Partition0"); //QFile dsk("//./Volume{e988ffc3-3512-11e3-99d8-806e6f6e6963}"); //QFile dsk("//./Volume{04bbc7e2-a450-11e3-a9d9-902b34d5484f}"); //QFile dsk("C:/out_2.bin"); if (!dsk.open(QIODevice::ReadOnly)) qDebug() << "Failed to open:" << dsk.errorString(); qDebug() << "Size:" << dsk.size() << "\n"; // Blank out image file QFile img(dst); img.open(QIODevice::WriteOnly); img.write(0); img.close(); // Read and write operations while (!dsk.atEnd()) { QByteArray readBytes = dsk.readLine(); qDebug() << "Reading: " << readBytes.size() << "\n"; QFile img(dst); if (!img.open(QIODevice::Append)) qDebug() << "Failed to open:" << img.errorString(); img.write(readBytes); } QTextStream(stdout) << "End\n"; I guess the real problem I'm having is how to open a volume with QFile in Windows. I tried a few variants, but to no avail.

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  • Ubuntu 12.04 on Amazon EC2: /dev/xvda1 will be checked for errors at next reboot?

    - by cwd
    I'm running the lastest Ubuntu 12.04 AMI (ami-a29943cb) from Canonical on Amazon EC2 and quite often when I log in I get the message: *** /dev/xvda1 will be checked for errors at next reboot *** I have read a bunch of documentation on this and seem to understand that every so many reboots (around 37 see Mount count / Maximum mount count below) Ubuntu wants to check a disk for errors. I can see that by using dumpe2fs -h /dev/xvda1 (reference) to get information such as: Last mounted on: / Filesystem UUID: 1ad27d06-4ecf-493d-bb19-4710c3caf924 Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Filesystem flags: signed_directory_hash Default mount options: (none) Filesystem state: clean Errors behavior: Continue Filesystem OS type: Linux Inode count: 524288 Block count: 2097152 Reserved block count: 104857 Free blocks: 1778055 Free inodes: 482659 First block: 0 Block size: 4096 Fragment size: 4096 Reserved GDT blocks: 511 Blocks per group: 32768 Fragments per group: 32768 Inodes per group: 8192 Inode blocks per group: 512 Flex block group size: 16 Filesystem created: Tue Apr 24 03:07:48 2012 Last mount time: Thu Nov 8 03:17:58 2012 Last write time: Tue Apr 24 03:08:52 2012 Mount count: 3 Maximum mount count: 37 Last checked: Tue Apr 24 03:07:48 2012 Check interval: 15552000 (6 months) Next check after: Sun Oct 21 03:07:48 2012 Lifetime writes: 2454 MB Reserved blocks uid: 0 (user root) Reserved blocks gid: 0 (group root) First inode: 11 Inode size: 256 Required extra isize: 28 Desired extra isize: 28 Journal inode: 8 Default directory hash: half_md4 Directory Hash Seed: 0a25e04c-6169-4d68-bfa6-a1acd8e39632 Journal backup: inode blocks Journal features: journal_incompat_revoke Journal size: 128M Journal length: 32768 Journal sequence: 0x0000158b Journal start: 1 I've tried these things to get rid of the message and usually the badblocks is what does it for me: Run this command and reboot: sudo touch /forcefsck Run badblocks to check the disk: badblocks /dev/sda1 Edit /etc/fstab and change the last "0" which is the fs_passno column accordingly and then reboot: The root filesystem should be specified with a fs_passno of 1, and other filesystems should have a fs_passno of 2. I don't understand: If this is a virtual drive shouldn't it be less prone to errors? Was the image created with one of the flags set? If not what is triggering it? Why is fs_passno set to 0 on Amazon EC2 Ubuntu images? This is not the first one that is like this.

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  • What approaches exist to setting up continent/country/city drop down menus?

    - by Dave
    How easy (or difficult) is it to have a Continent/Country/City drop down menu? Where one select from Drop Down Menus (for example): 1 - Europe 2 - UK 3 - London and then writes the Province/Area (for example: Essex). Realistically, how long should it take an experienced web developer to write the code of the above, as well as to link this selection to a Browse function and database storing? I do not have a geographical database yet and I am wondering what the fastest and cheapest way to add it to the drop down menu is. Is there any way to get that geographical database for free? I can see this type of geographical drop down menu in thousands of websites, but I am struggling as to how to implement it ASAP. Follow Up: Tks All x your answers and comments so far. I hear what you are saying. I understand that there are rare occasions of Countries with multiple (same) name Cities and that it might be disputable whether a Country belongs to a certain Continent/Region or not (see Russia x example, Europe or Asia?). Anyway, please take a look, for instance, at this website Sign UP screen http://www.couchsurfing.org/register.html My question then is: Where do I get that list (Country/Cities) and how do I create that _array? Manually copying it somewhere else (which would take me ages) or are there ready made lists that can be downloaded from somewhere for free?

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  • Pumpktris: The Tetris-Enabled Jack-o’-Lantern [Video]

    - by Jason Fitzpatrick
    You can carve a pumpkin, you might even go high-tech and wire it up with a few LEDs, but can you play Tetris on it? Check out this fully functional Tetris clone built into a jack-o’-lantern. The build comes to us courtesy of tinker Nathan at HaHaBird, who writes: One of my habits is to write down all the crazy, fleeting ideas I have, then go back to review later rather than judging right off the bat, or even worse, forgetting them. Earlier in the month I was looking through that idea notepad and found “Make Tetris Pumpkins” from sometime last year. My original plan had been to make forms to shape pumpkins into Tetris pieces as they grew, then stack them together for Halloween. Since Halloween was only a few weeks away and it was too late to start growing pumpkins, I thought “Why not make a pumpkin you can play Tetris on instead?” Watch the Pumpktris in action via the video above or hit up the link below to see exactly how he went about building it. Pumpktris [via Geek News Central] 6 Start Menu Replacements for Windows 8 What Is the Purpose of the “Do Not Cover This Hole” Hole on Hard Drives? How To Log Into The Desktop, Add a Start Menu, and Disable Hot Corners in Windows 8

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  • Event on SQL Server 2008 Disk IO and the new Complex Event Processing (StreamInsight) feature in R2

    - by tonyrogerson
    Allan Mitchell and myself are doing a double act, Allan is becoming one of the leading guys in the UK on StreamInsight and will give an introduction to this new exciting technology; on top of that I'll being talking about SQL Server Disk IO - well, "Disk" might not be relevant anymore because I'll be talking about SSD and IOFusion - basically I'll be talking about the underpinnings - making sure you understand and get it right, how to monitor etc... If you've any specific problems or questions just ping me an email [email protected]. To register for the event see: http://sqlserverfaq.com/events/217/SQL-Server-and-Disk-IO-File-GroupsFiles-SSDs-FusionIO-InRAM-DBs-Fragmentation-Tony-Rogerson-Complex-Event-Processing-Allan-Mitchell.aspx 18:15 SQL Server and Disk IOTony Rogerson, SQL Server MVPTony's Blog; Tony on TwitterIn this session Tony will talk about RAID levels, how SQL server writes to and reads from disk, the effect SSD has and will talk about other options for throughput enhancement like Fusion IO. He will look at the effect fragmentation has and how to minimise the impact, he will look at the File structure of a database and talk about what benefits multiple files and file groups bring. We will also touch on Database Mirroring and the effect that has on throughput, how to get a feeling for the throughput you should expect.19:15 Break19:45 Complex Event Processing (CEP)Allan Mitchell, SQL Server MVPhttp://sqlis.com/sqlisStreamInsight is Microsoft’s first foray into the world of Complex Event Processing (CEP) and Event Stream Processing (ESP).  In this session I want to show an introduction to this technology.  I will show how and why it is useful.  I will get us used to some new terminology but best of all I will show just how easy it is to start building your first CEP/ESP application.

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  • SQL SERVER – Identify Most Resource Intensive Queries – SQL in Sixty Seconds #028 – Video

    - by pinaldave
    During performance tuning conversation the very first question people often ask is what are the queries offending the server or in another word let us identify the queries which are the most resource intensive. The resources are often described as either Memory, CPU or IO. When we talk about the queries the same is applicable for them as well. The query which is doing lots of reads or writes are for sure resource intensive as well query which are taking maximum CPU time. Performance tuning is a very deep subject and we all have our own preference regarding what should be the first step to tuning and what should be looked with the salt of grain. Though there is no denying that a query which uses more resources than what it should be using for sure require tuning. There are many ways to do identify query using intense resources (e.g. Extended events etc) but in this one we will go by simple DMV. There is a small gotcha we all have to remember about usage of DMV is that it only brings back results from existing cache. So if you have a query which is very resource intensive but is not cached or if you have explicitly removed the query from the cache it will be not part of the result returned by this DMV. It is quite possible that a query is aged and removed from the cache if your cache is not huge. If your cache is large you may want to be careful in running this query during business hours as this query itself can be resource intensive. Get Script to identify resource intensive query from Here Related Tips in SQL in Sixty Seconds: SQL SERVER – Find Most Expensive Queries Using DMV Simple Example to Configure Resource Governor – Introduction to Resource Governor SQL SERVER – DMV – sys.dm_exec_query_optimizer_info – Statistics of Optimizer SQL SERVER – Wait Stats – Wait Types – Wait Queues – Day 0 of 28 Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Database, Pinal Dave, PostADay, SQL, SQL Authority, SQL in Sixty Seconds, SQL Query, SQL Scripts, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL, Technology, Video Tagged: Excel

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