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• Quantifying the effects of partition mis-alignment

  - by Matt

  I'm experiencing some significant performance issues on an NFS server. I've been reading up a bit on partition alignment, and I think I have my partitions mis-aligned. I can't find anything that tells me how to actually quantify the effects of mis-aligned partitions. Some of the general information I found suggests the performance penalty can be quite high (upwards of 60%) and others say it's negligible. What I want to do is determine if partition alignment is a factor in this server's performance problems or not; and if so, to what degree? So I'll put my info out here, and hopefully the community can confirm if my partitions are indeed mis-aligned, and if so, help me put a number to what the performance cost is. Server is a Dell R510 with dual E5620 CPUs and 8 GB RAM. There are eight 15k 2.5” 600 GB drives (Seagate ST3600057SS) configured in hardware RAID-6 with a single hot spare. RAID controller is a Dell PERC H700 w/512MB cache (Linux sees this as a LSI MegaSAS 9260). OS is CentOS 5.6, home directory partition is ext3, with options “rw,data=journal,usrquota”. I have the HW RAID configured to present two virtual disks to the OS: /dev/sda for the OS (boot, root and swap partitions), and /dev/sdb for a big NFS share: [root@lnxutil1 ~]# parted -s /dev/sda unit s print Model: DELL PERC H700 (scsi) Disk /dev/sda: 134217599s Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 63s 465884s 465822s primary ext2 boot 2 465885s 134207009s 133741125s primary lvm [root@lnxutil1 ~]# parted -s /dev/sdb unit s print Model: DELL PERC H700 (scsi) Disk /dev/sdb: 5720768639s Sector size (logical/physical): 512B/512B Partition Table: gpt Number Start End Size File system Name Flags 1 34s 5720768606s 5720768573s lvm Edit 1 Using the cfq IO scheduler (default for CentOS 5.6): # cat /sys/block/sd{a,b}/queue/scheduler noop anticipatory deadline [cfq] noop anticipatory deadline [cfq] Chunk size is the same as strip size, right? If so, then 64kB: # /opt/MegaCli -LDInfo -Lall -aALL -NoLog Adapter #0 Number of Virtual Disks: 2 Virtual Disk: 0 (target id: 0) Name:os RAID Level: Primary-6, Secondary-0, RAID Level Qualifier-3 Size:65535MB State: Optimal Stripe Size: 64kB Number Of Drives:7 Span Depth:1 Default Cache Policy: WriteBack, ReadAdaptive, Direct, No Write Cache if Bad BBU Current Cache Policy: WriteThrough, ReadAdaptive, Direct, No Write Cache if Bad BBU Access Policy: Read/Write Disk Cache Policy: Disk's Default Number of Spans: 1 Span: 0 - Number of PDs: 7 ... physical disk info removed for brevity ... Virtual Disk: 1 (target id: 1) Name:share RAID Level: Primary-6, Secondary-0, RAID Level Qualifier-3 Size:2793344MB State: Optimal Stripe Size: 64kB Number Of Drives:7 Span Depth:1 Default Cache Policy: WriteBack, ReadAdaptive, Direct, No Write Cache if Bad BBU Current Cache Policy: WriteThrough, ReadAdaptive, Direct, No Write Cache if Bad BBU Access Policy: Read/Write Disk Cache Policy: Disk's Default Number of Spans: 1 Span: 0 - Number of PDs: 7 If it's not obvious, virtual disk 0 corresponds to /dev/sda, for the OS; virtual disk 1 is /dev/sdb (the exported home directory tree).

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• High I/O latency with software RAID, LUKS encrypted and LVM partitioned KVM setup

  - by aef

  I found out a performance problems with a Mumble server, which I described in a previous question are caused by an I/O latency problem of unknown origin. As I have no idea what is causing this and how to further debug it, I'm asking for your ideas on the topic. I'm running a Hetzner EX4S root server as KVM hypervisor. The server is running Debian Wheezy Beta 4 and KVM virtualisation is utilized through LibVirt. The server has two different 3TB hard drives as one of the hard drives was replaced after S.M.A.R.T. errors were reported. The first hard disk is a Seagate Barracuda XT ST33000651AS (512 bytes logical, 4096 bytes physical sector size), the other one a Seagate Barracuda 7200.14 (AF) ST3000DM001-9YN166 (512 bytes logical and physical sector size). There are two Linux software RAID1 devices. One for the unencrypted boot partition and one as container for the encrypted rest, using both hard drives. Inside the latter RAID device lies an AES encrypted LUKS container. Inside the LUKS container there is a LVM physical volume. The hypervisor's VFS is split on three logical volumes on the described LVM physical volume: one for /, one for /home and one for swap. Here is a diagram of the block device configuration stack: sda (Physical HDD) - md0 (RAID1) - md1 (RAID1) sdb (Physical HDD) - md0 (RAID1) - md1 (RAID1) md0 (Boot RAID) - ext4 (/boot) md1 (Data RAID) - LUKS container - LVM Physical volume - LVM volume hypervisor-root - LVM volume hypervisor-home - LVM volume hypervisor-swap - … (Virtual machine volumes) The guest systems (virtual machines) are mostly running Debian Wheezy Beta 4 too. We have one additional Ubuntu Precise instance. They get their block devices from the LVM physical volume, too. The volumes are accessed through Virtio drivers in native writethrough mode. The IO scheduler (elevator) on both the hypervisor and the guest system is set to deadline instead of the default cfs as that happened to be the most performant setup according to our bonnie++ test series. The I/O latency problem is experienced not only inside the guest systems but is also affecting services running on the hypervisor system itself. The setup seems complex, but I'm sure that not the basic structure causes the latency problems, as my previous server ran four years with almost the same basic setup, without any of the performance problems. On the old setup the following things were different: Debian Lenny was the OS for both hypervisor and almost all guests Xen software virtualisation (therefore no Virtio, also) no LibVirt management Different hard drives, each 1.5TB in size (one of them was a Seagate Barracuda 7200.11 ST31500341AS, the other one I can't tell anymore) We had no IPv6 connectivity Neither in the hypervisor nor in guests we had noticable I/O latency problems According the the datasheets, the current hard drives and the one of the old machine have an average latency of 4.12ms.

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• Using DockPanel Suite's XML saving with My.Settings

  - by Cyclone

  In vb.net, how can I use SaveAsXML and LoadFromXML (DockPanel Suite functions) with My.Settings? I know there is a way to save it to a stream, but I don't know enough about System.IO to do this. DockPanel Suite: http://sourceforge.net/projects/dockpanelsuite/ I would very much prefer to store configuration using My.Settings instead of as an XML file. Thanks for the help! EDIT: Since the only person to answer so far has since deleted their answer, I feel I should explain further: Those two methods can both accept a stream object, but I have not used System.IO enough to know how to properly initialize a stream, let alone get a string out of a stream. EDIT: Googling has gotten me nowhere. EDIT: Still waiting for this. I've tried everything...

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• Python 3 with the range function

  - by Leif Andersen

  I can type in the following code in the terminal, and it works: for i in range(5): print(i) And it will print: 0 1 2 3 4 as expected. However, I tried to write a script that does a similar thing: print(current_chunk.data) read_chunk(file, current_chunk) numVerts, numFaces, numEdges = current_chunk.data print(current_chunk.data) print(numVerts) for vertex in range(numVerts): print("Hello World") current_chunk.data is gained from the following method: def read_chunk(file, chunk): line = file.readline() while line.startswith('#'): line = file.readline() chunk.data = line.split() The output for this is: ['OFF'] ['490', '518', '0'] 490 Traceback (most recent call last): File "/home/leif/src/install/linux2/.blender/scripts/io/import_scene_off.py", line 88, in execute load_off(self.properties.path, context) File "/home/leif/src/install/linux2/.blender/scripts/io/import_scene_off.py", line 68, in load_off for vertex in range(numVerts): TypeError: 'str' object cannot be interpreted as an integer So, why isn't it spitting out Hello World 490 times? Or is the 490 being thought of as a string? I opened the file like this: def load_off(filename, context): file = open(filename, 'r')

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• Need help manipulating WAV (RIFF) Files at a byte level

  - by Eric

  I'm writing an an application in C# that will record audio files (*.wav) and automatically tag and name them. Wave files are RIFF files (like AVI) which can contain meta data chunks in addition to the waveform data chunks. So now I'm trying to figure out how to read and write the RIFF meta data to and from recorded wave files. I'm using NAudio for recording the files, and asked on their forums as well on SO for way to read and write RIFF tags. While I received a number of good answers, none of the solutions allowed for reading and writing RIFF chunks as easily as I would like. But more importantly I have very little experience dealing with files at a byte level, and think this could be a good opportunity to learn. So now I want to try writing my own class(es) that can read in a RIFF file and allow meta data to be read, and written from the file. I've used streams in C#, but always with the entire stream at once. So now I'm little lost that I have to consider a file byte by byte. Specifically how would I go about removing or inserting bytes to and from the middle of a file? I've tried reading a file through a FileStream into a byte array (byte[]) as shown in the code below. System.IO.FileStream waveFileStream = System.IO.File.OpenRead(@"C:\sound.wav"); byte[] waveBytes = new byte[waveFileStream.Length]; waveFileStream.Read(waveBytes, 0, waveBytes.Length); And I could see through the Visual Studio debugger that the first four byte are the RIFF header of the file. But arrays are a pain to deal with when performing actions that change their size like inserting or removing values. So I was thinking I could then to the byte[] into a List like this. List<byte> list = waveBytes.ToList<byte>(); Which would make any manipulation of the file byte by byte a whole lot easier, but I'm worried I might be missing something like a class in the System.IO name-space that would make all this even easier. Am I on the right track, or is there a better way to do this? I should also mention that I'm not hugely concerned with performance, and would prefer not to deal with pointers or unsafe code blocks like this guy. If it helps at all here is a good article on the RIFF/WAV file format.

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• What is node.js?

  - by Jeffrey

  I don't fully get what node.js is all about. Maybe it's because I am mainly a web based business app developer. Can someone please explain what it is and the use of it? Thanks. My understanding so far is that: The programming model is event driven, especially the way it handles IO. It uses javascript and the parser is V8. It can be easily used to create concurrent server apps. Are my understandings correct? If yes, then what are the benefits of evented IO, is it just more for the concurrency stuffs? Also is the direction of node.js to become a framework like, javascript based (v8 based) programming model?

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• Package management fails in update-manager with gzip problems and compilation errors. U12.04LTS

  - by HarveyP

  Similar to but not the same as Package management system corrupted. Cannot install or remove packages. U12.04LTS (an earlier problem) with package management system. Followed all of L. D. James suggestions in his answer to no avail. This time as well as the gzip error I am also getting compilation errors. The difference may be due to a lack of compilation in my earlier problem so it may be the same error. The packages concerned are enumerated in the output from update-manager below. Also included below that is the output from apt-get -f install apt-get autoremove gives same output. Tried update without SSL updates - 9 to install and got "Unhandled Error in aptdaemon". Output number 3 below. One at a time - output 4 - is for firefox, first in the list of packages. Falls over at libssl1.0.0 despite deselection of it from update ... Tried apt-get install --reinstall dpkg which succeeded, apt-get install --reinstall tar and apt-get install --reinstall gzip both of which failed at libssl1.0.0 as ever. (as suggested by Subv3rsion elsewhere in this forum) Now cannot apt-get update with complete success even after changing server and apt-get clean - output number 5 below ... 1). Output from update-manager The following packages will be upgraded:<> firefox firefox-globalmenu firefox-locale-en libavcodec-extra-53 libavformat53 libavutil-extra-51 libjson0 libpostproc52 libssl1.0.0 libswscale2 openssl 11 to upgrade, 0 to newly install, 0 to remove and 0 not to upgrade.<br> Need to get 0 B/46.5 MB of archives. After this operation, 1,416 kB of additional disk space will be used.<br> Do you want to continue [Y/n]? y debconf: Perl may be unconfigured (Bareword "gensym" not allowed while "strict subs" in use at /usr/lib/perl/5.14/IO/Handle.pm line 67. BEGIN not safe after errors--compilation aborted at /usr/lib/perl/5.14/IO/Handle.pm line 366. Compilation failed in require at /usr/lib/perl/5.14/IO/Seekable.pm line 9. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/IO/Seekable.pm line 9. Compilation failed in require at /usr/lib/perl/5.14/IO/File.pm line 11. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/IO/File.pm line 11. Compilation failed in require at /usr/share/perl/5.14/FileHandle.pm line 9. Compilation failed in require at (eval 1) line 3. BEGIN failed--compilation aborted at (eval 1) line 3. ) -- aborting (Reading database ... 160575 files and directories currently installed.) Preparing to replace libssl1.0.0 1.0.1-4ubuntu5.14 (using .../libssl1.0.0_1.0.1-4ubuntu5.15_i386.deb) ... Unpacking replacement libssl1.0.0 ... dpkg-deb (subprocess): data: internal gzip read error: '<fd:4>: data error' dpkg-deb: error: subprocess <decompress> returned error exit status 2 dpkg: error processing /var/cache/apt/archives/libssl1.0.0_1.0.1-4ubuntu5.15_i386.deb (--unpack):<br> subprocess dpkg-deb --fsys-tarfile returned error exit status 2 No apport report written because MaxReports has already been reached Bareword "gensym" not allowed while "strict subs" in use at /usr/lib/perl/5.14/IO/Handle.pm line 67. BEGIN not safe after errors--compilation aborted at /usr/lib/perl/5.14/IO/Handle.pm line 366. Compilation failed in require at /usr/lib/perl/5.14/IO/Seekable.pm line 9. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/IO/Seekable.pm line 9. Compilation failed in require at /usr/lib/perl/5.14/IO/File.pm line 11. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/IO/File.pm line 11. Compilation failed in require at /usr/share/perl/5.14/FileHandle.pm line 9. Compilation failed in require at /usr/share/perl5/Debconf/Template.pm line 8. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Template.pm line 8. Compilation failed in require at /usr/share/perl5/Debconf/Question.pm line 8. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Question.pm line 8. Compilation failed in require at /usr/share/perl5/Debconf/Config.pm line 7. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Config.pm line 7. Compilation failed in require at /usr/share/perl5/Debconf/Log.pm line 10. Compilation failed in require at /usr/share/perl5/Debconf/Db.pm line 7. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Db.pm line 7. Compilation failed in require at /usr/share/debconf/frontend line 6. BEGIN failed--compilation aborted at /usr/share/debconf/frontend line 6. dpkg: error whale cleanang up: subprgcess installed post-installation script returned error exit status 2 Errors were encountered while processing: /var/cache/apt/archives/libssl1.0.0_1.0.1-4ubuntu5.15_i386.deb E: Sub-process /usr/bin/dpkg returned an error code (1) 2). Output from install -f harveyp@harveyp:~$ sudo apt-get -f install [sudo] password for harveyp: Reading package lists... Done Building dependency tree Reading state information... Done 0 to upgrade, 0 to newly install, 0 to remove and 11 not to upgrade. 1 not fully installed or removed.<br> After this operation, 0 B of additional disk space will be used. E: Internal Error, No file name for libssl1.0.0 3). Unhandled error from aptdaemon Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 1045, in _simulate trans.unauthenticated = self.__simulate(trans) File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 1160, in __simulate unauthenticated = self._get_unauthenticated() File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 347, in _get_unauthenticated for pkg in self._iterate_packages(): File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 1356, in _iterate_packages for enum, pkg in enumerate(self._cache): File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 216, in __iter__ yield self[pkgname] File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 201, in __getitem__ pkg = self._weakref[key] = Package(self, self._cache[key]) KeyError: 'librqrcode-rubq-doc 4). output from update of firefox installArchives() failed: Error in function: < Setting up libssl1.0.0 (1.0.1-4ubuntu5.14) ... Bareword "gensym" not allowed while "strict subs" in use at /usr/lib/perl/5.14/IO/Handle.pm line 67. BEGIN not safe after errors--compilation aborted at /usr/lib/perl/5.14/IO/Handle.pm line 366. Compilation failed in require at /usr/lib/perl/5.14/IO/Seekable.pm line 9. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/IO/Seekable.pm line 9. Compilation failed in require at /usr/lib/perl/5.14/IO/File.pm line 11. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/IO/File.pm line 11. Compilation failed in require at /usr/share/perl/5.14/FileHandle.pm line 9. Compilation failed in require at /usr/share/perl5/Debconf/Template.pm line 8. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Template.pm line 8. Compilation failed in require at /usr/share/perl5/Debconf/Question.pm line 8. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Question.pm line 8. Compilation failed in require at /usr/share/perl5/Debconf/Config.pm line 7. BEGIN failed--compilation aborted at /usr/share/perl5/Debconf/Config.pm line 7. Compilation failed in require at /usr/share/perl5/Debconf/Log.pm line 10. 5. output from apt-get update ...snip ... Hit http://ubuntu-archive.mirrors.free.org precise-security/multiverse Translation-en Hit http://ubuntu-archive.mirrors.free.org precise-security/restricted Translation-en Hit http://ubuntu-archive.mirrors.free.org precise-security/universe Translation-en Fetched 368 kB in 6s (59.5 kB/s) W: Failed to fetch gzip:/var/lib/apt/lists/partial/ubuntu-archive.mirrors.free.org_ubuntu_dists_precise_universe_source_Sources Hash Sum mismatch E: Some index files failed to download. They have been ignored, or old ones used instead.

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• aio_write on linux with rtkaio is sometimes long

  - by Drakosha

  I'm using async io on linux with rtkaio library. In my tests everything works perfectly, but, in my real application i see that aio_write which is supposed to return very fast, is very slow. It can take more than 100 milis to write a 128KB to a O_DIRECT padded file. Both my test and the application use same I/O size, i check on the same file system (GFS). I added counting and i see that there are about 50% of async io operations that are short (shorter then 2 milis) and 50% that are long (longer than 2 milis). I also checked that the test and the application both use the same rtkaio library. I'm pretty lost, anyone any ideas where should i look? Another my related question: http://stackoverflow.com/questions/1799537/proc-sys-fs-aio-nr-is-never-higher-than-1024-aio-on-linux

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• Drawbacks with reading and writing a big file to or from disk at once instead of small chunks?

  - by Johann Gerell

  I work mainly on Windows and Windows CE based systems, where CreateFile, ReadFile and WriteFile are the work horses, no matter if I'm in native Win32 land or in managed .Net land. I have so far never had any obvious problem writing or reading big files in one chunk, as opposed to looping until several smaller chunks are processed. I usually delegate the IO work to a background thread that notifies me when it's done. But looking at file IO tutorials or "textbook examples", I often find the "loop with small chunks" used without any explanation of why it's used instead of the more obvious (I dare to say!) "do it all at once". Are there any drawbacks to the way I do that I haven't understood?

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• Java: opening and reading from a file without locking it.

  - by rogue780

  I need to be able to mimic 'tail -f' with Java. I'm trying to read a log file as it's being written by another process, but when I open the file to read it, it locks the file and the other process can't write to it anymore. Any help would be greatly appreciated! Here is the code that I'm using currently: public void read(){ Scanner fp = null; try{ fp = new Scanner(new FileReader(this.filename)); fp.useDelimiter("\n"); }catch(java.io.FileNotFoundException e){ System.out.println("java.io.FileNotFoundException e"); } while(true){ if(fp.hasNext()){ this.parse(fp.next()); } } }

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• Ruby: Read large data from stdout and stderr of an external process on Windows

  - by BinaryMuse

  Greetings, all, I need to run a potentially long-running process from Ruby on Windows and subsequently capture and parse the data from the external process's standard output and error. A large amount of data can be sent to each, but I am only necessarily interested in one line at a time (not capturing and storing the whole of the output). After a bit of research, I found that the Open3 class would take care of executing the process and giving me IO objects connected to the process's standard output and error (via popen3). Open3.popen3("external-program.bat") do |stdin, out, err, thread| # Step3.profit() ? end However, I'm not sure how to continually read from both streams without blocking the program. Since calling IO#readlines on out or err when a lot of data has been sent results in a memory allocation error, I'm trying to continuously check both streams for available input, but not having much luck with any of my implementations. Thanks in advance for any advice!

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• In Java how do a read an input stream in to a string?

  - by Johnny Maelstrom

  If you have an java.io.InputStream object how should you process that object and produce a string.

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• Hard drive write speed - finding a lighter antivirus?

  - by Shingetsu

  I recently have been getting a lot of system lag here (for example, the mouse and the display in general take about 15 seconds to react in the worst cases). After a lot of monitoring the resources, I found that the problem mainly happens when too much Disk I/O is being done. Three culprits have been identified: My browser had the highest write I/O with 35,000,000 I/O Write Bytes. Steam had the highest read I/O (when IDLE!!!) with 106,000,000 I/O Read Bytes. My antivirus (in both cases I will soon mention) was the runner up in both cases with: 30,000,000ish write and 80,000,000ish read. The first AV I had was Avast! which I had liked on my previous system. After noticing it taking so much I/O I switched to Panda (supposing it wouldn't use TOO much during idle phase). However it only used a bit less I/O. Just a lot less memory and cpu and somewhat more network. My browser at the moment is Maxthon 3 (which I like a lot). Before this I was running chrome which had similar data and much higher cpu when running in the background was enabled. I'm not going to be running steam all the time and there aren't many alternatives to it. I like my browser very much, but I AM willing to switch if there's an obvious problem (I'm in programming, however I'm not a very good sysadmin, especially not when it comes to windows). Finally, my system almost stops lagging when I turn off the antivirus (and preferably steam) (some remains but once in every 5-6 hours for a few seconds so it isn't a big problem). My question (has a few parts): Is it possible to configure steam to lower it's I/O usage? (and maybe network while we're at it?) Which antivirus (very preferably free) uses lowest I/O while idle (I leave PC alone during active scans so that isn't a problem). Is there an obvious problem with my current browser and, if so, is there a way to fix it or should I switch and, if so, to what? (P.S. I've been on FFox for some time too). Info on system: Windows 7 (32 bit T_T, I am getting a new one in a few months but I want to keep using system during that time though). Hard Drive (main) is a Raid0. (Also have an external 1TB one which contains steam (and steam alone). As such it doesn't get used by much anything other than steam and isn't a very large problem. However steam still uses some I/O of registry) CPU: Intel(R) Core(TM)2 CPU [email protected] RAM: 6GB (3.25GB usable) (this and CPU have little effect as shown in next section) Additional info: Memory usage during problematic times: 44% CPU usage during problematic times: 35% Page File: main drive: system managed. 1TB drive: none. The current system I'm using is about 6 years old and is mainly a place holder while I await the new one in a few months. Final words: this is my 1st post on Super User (this question wouldn't feel right on Stack Overflow where I usually stay). If it doesn't have it's place here please tell me. If anything is wrong with it, same. Edit Technically I'm looking for a live thread detection program with minimal IO usage. I already have good active scan capability: Kaspersky (the free scanner uses the paid database) and MalwareBytes. Edit 2 Noticed another one, it seems that windows media player has been using stuff even when off! Turning it off and restarting now. If the problem is fixed I'll tell you guys. The reason I didn't notice it before was because I didn't have resource manager in front of me at the MOMENT of the problem. Now I did and it was at the very top of the list!

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• How to close IOs?

  - by blackdog

  when i managed IO, i found a problem. i used to close it like this: try { // my code } catch (Exception e) { // my code } finally{ if (is != null) { is.close(); } } but the close method also would throw exception. if i have more than one IO, i have to close all of them. so the code maybe like this: try { // my code } catch (Exception e) { // my code } finally{ if (is1 != null) { is1.close(); } if(is2 != null{ is2.close(); } // many IOs } if is1.close() throws an exception, is2, is3 would not close itself. So i have to type many try-catch-finally to control them. is there other way to solve the problem?

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• Is there a java library / package analogous to <stdio.h>?

  - by Roboprog

  I have been doing Java on and off for about 14 years, and almost nothing else the last 6 years or so. I really hate the java.io package -- its legion of subclasses and adapters. I do like exceptions, rather than having to always poll "errno" and the like, but I could surely live without declared exceptions. Is there anything that functions like the Unix/ANSI stdio.h routines in C? I know we will never be rid of java.io and its conventions until java itself is retired, as they have metastasized throughout the many frameworks that have accreted to java. That said, I would like something that works kind of like this (let's call it package javax.stdio): Have a main utility class, perhaps FileStar, that can read and write files (or pipes), either text or binary, either sequentially or random access, with constructors that mimic fopen() and popen(). This class should have a load of useful methods that do things like fread(), fwrite(), fgets(), fputs(), fseek(), and whatever else (fprintf()?). Methods that are incompatible with the open/construct mode simply throw up (just like some of the collections classes/methods do when restricted). Then, have a bunch of interfaces that suggest how you intend to use the stream once you have created it: Sequential, RandomAccess, ReadOnly, WriteOnly, Text, Binary, plus combinations of these that make sense. Perhaps even have methods to return the appropriate type-cast (interface), throwing up if you have asked for something incompatible. For extra flavor, skip the declared exceptions -- e.g. - javax.stdio.IOException extends RuntimeException. Is there an open source project like this floating around?

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• Return value from Object match

  - by Hito_kun

  I'm, by no means, JS fluent, so forgive me if im asking for some really basic stuff, but I've not being able to find a proper answer to my question. Im writting my first Node.js (plus Extra Framework and Socket.io) app and Im having some fun setting up the server side of a FB-like messenger (surprise!!!). So, let's say I have this data structure to store online users(This is a JSON Array, but I'm not sure it is the best way to do it or should I go with Javascript Objects): [ { "site": 45, "users": [ { "idUser": 5, "idSocket": "qwe87r7w8qwe", "name": "Carlos Ray Norris" }, { "idUser": 6, "idSocket": "v8d9d0fgfs7d", "name": "John Connor" } ] }, { "site": 48, "users": [ { "idUser": 22, "idSocket": "qwe87r7w8qwe", "name": "David Bowie" }, { "idUser": 23, "idSocket": "v8d9d0fgfs7d", "name": "Barack H. Obama" } ] } ] What I want to do is to search in the array for x value given y. In this case, retrieving the idSocket knowing the idUser WITHOUT having to run through the array values. So I have basically 2 questions: first, what would be the proper way to store users online? and secondly, how to find values matching with the values I already know (find the idSocket that has a given idUser). I would like a pure JS approach(or using some of the tools given by Node, Socket.io or Express), but if that's not possible then I can look for some JQuery.

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• Disk performance below expectations

  - by paulH

  this is a follow-up to a previous question that I asked (Two servers with inconsistent disk speed). I have a PowerEdge R510 server with a PERC H700 integrated RAID controller (call this Server B) that was built using eight disks with 3Gb/s bandwidth that I was comparing with an almost identical server (call this Server A) that was built using four disks with 6Gb/s bandwidth. Server A had much better I/O rates than Server B. Once I discovered the difference with the disks, I had Server A rebuilt with faster 6Gbps disks. Unfortunately this resulted in no increase in the performance of the disks. Expecting that there must be some other configuration difference between the servers, we took the 6Gbps disks out of Server A and put them in Server B. This also resulted in no increase in the performance of the disks. We now have two identical servers built, with the exception that one is built with six 6Gbps disks and the other with eight 3Gbps disks, and the I/O rates of the disks is pretty much identical. This suggests that there is some bottleneck other than the disks, but I cannot understand how Server B originally had better I/O that has subsequently been 'lost'. Comparative I/O information below, as measured by SQLIO. The same parameters were used for each test. It's not the actual numbers that are significant but rather the variations between systems. In each case D: is a 2 disk RAID 1 volume, and E: is a 4 disk RAID 10 volume (apart from the original Server A, where E: was a 2 disk RAID 0 volume). Server A (original setup with 6Gpbs disks) D: Read (MB/s) 63 MB/s D: Write (MB/s) 170 MB/s E: Read (MB/s) 68 MB/s E: Write (MB/s) 320 MB/s Server B (original setup with 3Gpbs disks) D: Read (MB/s) 52 MB/s D: Write (MB/s) 88 MB/s E: Read (MB/s) 112 MB/s E: Write (MB/s) 130 MB/s Server A (new setup with 3Gpbs disks) D: Read (MB/s) 55 MB/s D: Write (MB/s) 85 MB/s E: Read (MB/s) 67 MB/s E: Write (MB/s) 180 MB/s Server B (new setup with 6Gpbs disks) D: Read (MB/s) 61 MB/s D: Write (MB/s) 95 MB/s E: Read (MB/s) 69 MB/s E: Write (MB/s) 180 MB/s Can anybody suggest any ideas what is going on here? The drives in use are as follows: Dell Seagate F617N ST3300657SS 300GB 15K RPM SAS Dell Hitachi HUS156030VLS600 300GB 3.5 inch 15000rpm 6GB SAS Hitachi Hus153030vls300 300GB Server SAS Dell ST3146855SS Seagate 3.5 inch 146GB 15K SAS

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• Delay before download starts when serving files using nginx

  - by glumbo

  I am currently using nginx to serve downloads off my website. Users sometimes need to wait about 5 seconds before their download starts after clicking a download link. I'm not sure if I need to start using raid 10 (I'm currently using raid 50) or if this is a problem with my nginx configuration. I am also on a 1gbit line but download sometimes go as low as 10kB/s. My server: Dual Xeon 5620 CPU, 12x2TB drives with 8GB ram. This is my nginx.conf #user nobody; worker_processes 12; worker_rlimit_nofile 10240; worker_rlimit_sigpending 32768; error_log logs/error.log crit; #pid logs/nginx.pid; events { worker_connections 2048; } http { include mime.types; default_type application/octet-stream; access_log off; limit_conn_log_level info; log_format xfs '$arg_id|$arg_usr|$remote_addr|$body_bytes_sent|$status'; #sendfile on; #tcp_nopush on; reset_timedout_connection on; server_tokens off; autoindex off; keepalive_timeout 0; #keepalive_timeout 65; limit_zone one $binary_remote_addr 10m; perl_modules perl; perl_require download.pm;

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• Measuring 'total bytes written' under Linux

  - by badnews

  We're quite interested in exploring the possibility of using SSD drives in a server environment. However, one thing that we need to establish is expected drive longevity. According to this article manufacturer's are reporting drive endurance in terms of 'total bytes written' (TBW). E.g. from that article a Crucial C400 SSD is rated at 72TB TBW. Do any scripts/tools exist under the Linux ecosystem to help us measure TBW? (and then make a more educated decision on the feasibility of using SSD drives)

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• Bad I/O scheduler?

  - by user62367

  os: up-to-date Fedora 14. Working as a "normal desktop". It's doing very well, but if i start VirtualBox, and e.g.: install a guest on it, it just "freezez". I mean if there are disk activities on a VirtualBox guest, then the computer becomes unrespondable..even the mouse is laggin for about 50 minutes.. What could be the bottleneck? What could be the problem? If anyone has any tips/howtos to speed it up, please help! It has a normal 2,5" HDD, with 5400 RPM. Does it worth for me if i buy a 2,5" HDD with 7200 RPM? T7200 cpu, 4 GByte RAM, "vm.swappiness = 0". Thank you!

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• Different block sizes for partition and underlying logical disk on HP Raid Controller (Linux)

  - by Wawrzek

  Following links collected in this thread I started to check blockdev and found the following output indicating different sizes for partition c0d9p1 and the underlying device (c0d9): [root@machine ~]# blockdev --report /dev/cciss/c0d9 RO RA SSZ BSZ StartSec Size Device rw 256 512 4096 0 3906963632 /dev/cciss/c0d9 [root@machine ~]# blockdev --report /dev/cciss/c0d9p1 RO RA SSZ BSZ StartSec Size Device rw 256 512 2048 1 3906959039 /dev/cciss/c0d9p1 We have a lot of small files, so yes the block size is smaller than normal. The device is a logical driver on an HP P410 raid controller, simple disk without any raid - RAID 0 on one disk to be precise. (Please note that above configuration is a feature not a bug). Therefore, I have the following questions. Can the above discrepancy in the block size affect disk performance? Can I control the block size using hpacucli?

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• How to identify heavy write to disk?

  - by Darth

  I have this problem with server running CakePHP application. The server is insanely slow, I first thought that it's application problem, but then I found constant 5-6MB/s write to disk. What is the easiest way to find cause of such a heavy write? The server is running Gentoo.

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• I/O intensive MySql server on Amazon AWS

  - by rhossi

  We recently moved from a traditional Data Center to cloud computing on AWS. We are developing a product in partnership with another company, and we need to create a database server for the product we'll release. I have been using Amazon Web Services for the past 3 years, but this is the first time I received a spec with this very specific hardware configuration. I know there are trade-offs and that real hardware will always be faster than virtual machines, and knowing that fact forehand, what would you recommend? 1) Amazon EC2? 2) Amazon RDS? 3) Something else? 4) Forget it baby, stick to the real hardware Here is the hardware requirements This server will be focused on I/O and MySQL for the statistics, memory size and disk space for the images hosting. Server 1 I/O The very main part on this server will be I/O processing, FusionIO cards have proven themselves extremely efficient, this is currently the best you can have in this domain. o Fusion ioDrive2 MLC 365GB (http://www.fusionio.com/load/-media-/1m66wu/docsLibrary/FIO_ioDrive2_Datasheet.pdf) CPU MySQL will use less CPU cores than Apache but it will use them very hard, the E7 family has 30M Cache L3 wichi provide boost performance : o 1x Intel E7-2870 will be ok. Storage SAS will be good enough in terms of performance, especially considering the space required. o RAID 10 of 4 x SAS 10k or 15k for a total available space of 512 GB. Memory o 64 GB minimum is required on this server considering the size of the statistics database. Warning: the statistics database will grow quickly, if possible consider starting with 128 GB directly, it will help. This server will be focused on I/O and MySQL for the statistics, memory size and disk space for the images hosting. Server 2 I/O The very main part on this server will be I/O processing, FusionIO cards have proven themselves extremely efficient, this is currently the best you can have in this domain. o Fusion ioDrive2 MLC 365GB (http://www.fusionio.com/load/-media-/1m66wu/docsLibrary/FIO_ioDrive2_Datasheet.pdf) CPU MySQL will use less CPU cores than Apache but it will use them very hard, the E7 family has 30M Cache L3 wichi provide boost performance : o 1x Intel E7-2870 will be ok. Storage SAS will be good enough in terms of performance, especially considering the space required. o RAID 10 of 4 x SAS 10k or 15k for a total available space of 512 GB. Memory o 64 GB minimum is required on this server considering the size of the statistics database. Warning: the statistics database will grow quickly, if possible consider starting with 128 GB directly, it will help. Thanks in advance. Best,

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• I/O APIC on Virtualbox

  - by RidDeBakTiYar

  I'm trying to use the PIT to do APIC timer calibration, and I want to use the PIT through I/O APIC instead of PIC. On Bochs I get interrupts from the PIT at the asked frequency from the I/O APIC, while on Virtualbox I can't receive a single interrupt. It must be an I/O APIC configuration problem because as I unmask the first PIC entry, the IRQ fires. However that's not what I want. Can you imagine any possible condition that wouldn't make Virtualbox fire the IRQ? I'm not assuming single I/O APIC configuration (even though Virtualbox has only 1). I'm not assuming identity mappings between ISA IRQs and I/O APIC GSIs (using ACPI MADT table to get I/O APIC base address and Int override). I'm setting the Trigger Mode and Polarity bits correctly (on Virtualbox they are set as '00 - default' which means edge high right?). I'm putting the BSP APIC ID into the Destination field (using Physical destination) and vector 0x20. Being the BSP APIC ID 0 on Virtualbox, it ends up with 0x0000000000000020 written to the IOREDTBL. And, just in case I'm getting the wrong values from the Interrupt Override descriptor, I'm setting this value to all the IOREDTBL entries (I know this is very very bad, and it wont be kept as I understand what's going on). The only thing I didn't check out is Local APIC configuration. Actually I'm not writing any value to the BSP LAPIC. Just reading the APIC ID and using it to boot APs through IPIs. And obviously I'm setting bit 11 in the IA32_APIC_BASE MSR to enable the LAPIC. Any ideas? Thanks in advance.

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• Will adding a SSD cache device to my ZFS storage improve performance?

  - by Sysadminicus

  The server has 4GB of RAM and my zpool is made up of 15.5k SAS drives arranged like this: NAME STATE READ WRITE CKSUM tank ONLINE 0 0 0 raidz1-0 ONLINE 0 0 0 c0t2d0 ONLINE 0 0 0 c0t3d0 ONLINE 0 0 0 c0t4d0 ONLINE 0 0 0 c0t5d0 ONLINE 0 0 0 c0t6d0 ONLINE 0 0 0 c0t7d0 ONLINE 0 0 0 c0t8d0 ONLINE 0 0 0 raidz1-1 ONLINE 0 0 0 c0t10d0 ONLINE 0 0 0 c0t11d0 ONLINE 0 0 0 c0t12d0 ONLINE 0 0 0 c0t13d0 ONLINE 0 0 0 c0t14d0 ONLINE 0 0 0 spares c0t9d0 AVAIL c0t1d0 AVAIL The primary use is as an NFS store for a couple VMWare ESXi servers. I can't do any "true" benchmarks because this is a production system (no budget for test systems), but using dd and bonnie++ I can't get more than ~40-50MB/s writes and ~70-90MB/s reads. It seems I should be able to do much better, but I'm not sure where to optimize. Based on what I've read, I think dropping in a OCZ Vertex 2 Pro SSD as my L2ARC is going to be the best bang-for-the-buck to improve througput. Is there something else I should be looking into to help performance? If not... How do I know how big a cache device I need? Am I safe with only a single SSD as my cache device?

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