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• Optimizing a large iteration of PHP objects (EAV-based)

  - by Aron Rotteveel

  I am currently working on a project that utilizes the EAV model. This turns out to work quite well, but like many others I am now stumbling upon some performance issues. The data set in this particular case consists of aproximately 2500 entities, each with aprox. 150 attributes. Each entity and each attribute is represented by a PHP-object. Since most parts of the application only iterate through a filtered set of entities, we have not had very large issues yet. Now, however, I am working on an algorithm that requires iteration over the entire dataset, which causes a major impact on performance. This information is perhaps not very much to work with, but since this is an architectural problem, I am hoping for a architectural pattern to help me on the way as well. Each entity, including it's attributes takes up aprox. 500KB of memory.

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• To store images from UIGetScreenImage() in NSMutable Array

  - by sujyanarayan

  Hi, I'm getting images from UIGetScreenImage() and storing directly in mutable array like:- image = [UIImage imageWithScreenContents]; [array addObject:image]; [image release]; I've set this code in timer so I cant use UIImagePNGRepresentation() to store as NSData as it reduces the performance. I want to use this array directly after sometime i.e after capturing 1000 images in 100 seconds. When I use the code below:- UIImage *im = [[UIImage alloc] init]; im = [array objectAtIndex:i]; UIImageWriteToSavedPhotosAlbum(im, nil, nil, nil); the application crashes. And I dont want to use UIImagePNG or JPGRepresentation() in timer as it reduces performance. My problem is how to use this array so that it is converted into image. If anybody has idea related to it please share with me. Thanks in Advance.

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• What is the best virtual grid for Winforms Csharp

  - by oo

  i am looking for both performance as well as ease of learning curve. thoughts?

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• silverlight for .NET / CLR based numerical computing on osx

  - by Jonathan Shore

  I'm interested in using F# for numerical work, but my platforms are not windows based. Mono still has a significant performance penalty for programs that generate a significant amount of short-lived objects (as would be typical for functional languages). Silverlight is available on OSX. I had seen some reference indicating that assemblies compiled in the usual way could not be referenced, but not clear on the details. I'm not interested in UIs, but wondering whether could use the VM bundled with silverlight effectively for execution? I would want to be able to reference a large library of numerical models I already have in java (cross-compiled via IKVM to .NET assemblies) and a new codebase written in F#. My hope would be that the silverlight VM on OSX has good performance and can reference external assemblies and native libraries. Is this doable?

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• Java object caching, which is faster, reading from a file or from a remote machine?

  - by Kumar225

  I am at a point where I need to take the decision on what to do when caching of objects reaches the configured threshold. Should I store the objects in a indexed file (like provided by JCS) and read them from the file (file IO) when required or have the object stored in a distributed cache (network, serialization, deserialization) We are using Solaris as OS. ============================ Adding some more information. I have this question so as to determine if I can switch to distributed caching. The remote server which will have cache will have more memory and better disk and this remote server will only be used for caching. One of the problems we cannot increase the locally cached objects is , it stores the cached objects in JVM heap which has limited memory(using 32bit JVM). ======================================================================== Thanks, we finally ended up choosing Coherence as our Cache product. This provides many cache configuration topologies, in process vs remote vs disk ..etc.

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• Assert parameters in a table-valued UDF

  - by Clay Lenhart

  Is there a way to create "asserts" on the parameters of a table-valued UDF. I'd like to use a table-valued UDF for performance reasons, however I know that certain parameter combinations (like start and end dates that are more than a month apart) will cause performance issues on the server for all users. End users query the database via Excel using UDFs. UDFs (and table-valued UDFs in particular) are useful when the data is too large for Excel. Users write simple SQL queries that categorizes the data into groups to reduce the number of rows. For example, the user may be interested in weekly aggregates rather than hourly ones. Users write a group by SELECT statement to reduce the rows by 24x7=168 times. I know I can write RAISERROR statements in multistatement UDFs, but table-valued UDFs are integrated in the query optimizer so these queries are more efficient with table-valued UDFs. So, can I define assertions on the parameters passed to a table-valued UDF?

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• LNK1106 with big binary resource

  - by E Dominique

  I have a rather huge .dat-file (896MB) included as a BIN resource in my project. Now I get a LNK1106 link error ("fatal error LNK1106: invalid file or disk full: cannot seek to 0x382A3920".) I use Visual Studio 2005 under Windows XP, and have tried on a 4GB RAM machine with high Virtual Memory settings and lots of disk space. I have tried a number of different optimization flags, but to no avail. Does anyone have a clue? EDIT: I have narrowed it down to a specific size of the compiled resource. If the .res file is 544078588 bytes (about 518.9MB) or larger, the error occurs. If it is smaller it works just fine. Still no solution, though...

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• Any good interview Questions to ask a sybase dba.

  - by scot

  Hi, I am a java developer and i will be interviewing sybase dbas along with my boss. I know some basic stuff about sybase. Iam looking for good interview questions that i can ask for a sybase dba. they will be having a min of 4 years of experience. I am looking for them to have really good knowledge in performance and tuning related areas like how to measure database performance and suggest ways to improve database design or sybase configuration etc. Help much appreciated. BR

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• Why Tokyo Tyrant so slow

  - by Tantra

  I have follow situation tyrant server lunched on freebsd host, like this: ttserver -uas -log /data/tyrant/1.log -sid 1 -thnum 8 -tout 5 /data/tyrant/data/1.tct And i try to communicate this server on windows from python and pyrant-0.3.5: like this: import pyrant; import time; t = pyrant.Tyrant(host="192.168.0.220", port=1978); tbegin = time.time(); for i in xrange(4000000): if i and ((i % 10000) == 0): print time.time() - tbegin; tbegin = time.time(); t[i] = {"text": "ruslan text", "value": i}; and have i think very slow performance about 5-6 per 10,000 records. But if i start this code on the same machine like server(ttserver). Performance are good - about 0.5 sec per 10,000 records What i must do to workaround this problem?

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• Popularity Algorithm - SQL / Django

  - by RadiantHex

  Hi folks, I've been looking into popularity algorithms used on sites such as Reddit, Digg and even Stackoverflow. Reddit algorithm: t = (time of entry post) - (Dec 8, 2005) x = upvotes - downvotes y = {1 if x > 0, 0 if x = 0, -1 if x < 0) z = {1 if x < 0, otherwise x} log(z) + (y * t)/45000 I have always performed simple ordering within SQL, I'm wondering how I should deal with such ordering. Should it be used to define a table, or could I build an SQL with the ordering within the formula (without hindering performance)? I am also wondering, if it is possible to use multiple ordering algorithms in different occasions, without incurring into performance problems. I'm using Django and PostgreSQL. Help would be much appreciated! ^^

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• Difference between Apache Tapestry and Apache Wicket

  - by Stephan Schmidt

  Apache Wicket ( http://wicket.apache.org/ ) and Apache Tapestry ( http://wicket.apache.org/ ) are both component oriented web frameworks - contrary to action based frameworks like Stripes - by the Apache Foundation. Both allow you to build your application from components in Java. They both look very similar to me. What are the differences between those two frameworks? Has someone experience in both? Specifically: How is their performance, how much can state handling be customized, can they be used stateless? What is the difference in their component model? What would you choose for which applications? How do they integrate with Guice, Spring, JSR 299? Edit: I have read the documentation for both and I have used both. The questions cannot be answered sufficently from reading the documentation, but from the experience from using these for some time, e.g. how to use Wicket in a stateless mode for high performance sites. Thanks.

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• How do I merge a local branch into TFS

  - by Johnny

  hi, I did a stupid thing and branched my project on my local disk instead of doing it on the TFS. So now I have two projects on my disk: the old one which has TFS bindings and the new, which doesn't. I want to merge those changes back into the TFS project. How would I go about doing that? I can't do Compare because my local branch has no TFS bindings. There should be some way to compare the differences between the two projects locally and then meld the differences into the old project and check-in, but I can't find an easy way of doing that. Any other solutions?

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• Using SqlCacheDependency to get real time updates? - ASP.NET

  - by user102533

  I would like to display real time updates on a web page (based on a status field in a database table that is altered by an external process). Based on my research, there are several ways of doing this. Long Polling (Comet) - This seems to be complex to implement Regular Polling - I can have an AJAX method trigger a database hit every 5seconds to get the current status. But I fear this will have performance issues. Then I read about using SqlCacheDependency - basically the cache gets invalidated based on a field in the table. I am assuming I can use the event trigerred when the cache is invalidated to show the new update to the user? What's an easy solution that will not have performance issues? anyone?

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• Are there any free .NET OCR libraries that will perform OCR on an application window directly?

  - by Kelsey

  I am looking for a free .NET OCR library that will be able to do OCR on a given application window or even a image in memory (I can take a snapshot of the application window myself). I have looked at tessnet2 and MODI but both require an image located on disk. I need to use OCR because the application I am trying to write a script for does some wacky stuff that cannot be read using windows API and I need to scrape data from the screen. I have tested both of tessnet2 and MODI and they both can read the text mostly but because this has to run in an enviroment that will not be able to write to disk, I need it to be able to read directly from the applciation window or some type of memory stream. I am thinking OCR is my only soution but there could be other methods that I am not thinking of. Suggestions?

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• How to set that compiler flag?

  - by mystify

  Shark told me this: This instruction is the start of a loop that is not aligned to a 16-byte address boundary. For optimal performance, you should align the start of a hot loop using a compiler directive. With gcc 3.3 or later, use the -falign-loops=16 compiler flag. for (int i=0; i < 4; i++) { // line with the info //...code } How would I set that flag, and does it really improve performance?

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• What are some best practises and "rules of thumb" for creating database indexes?

  - by Ash

  I have an app, which cycles through a huge number of records in a database table and performs a number of SQL and .Net operations on records within that database (currently I am using Castle.ActiveRecord on PostgreSQL). I added some basic btree indexes on a couple of the feilds, and as you would expect, the peformance of the SQL operations increased substantially. Wanting to make the most of dbms performance I want to make some better educated choices about what I should index on all my projects. I understand that there is a detrement to performance when doing inserts (as the database needs to update the index, as well as the data), but what suggestions and best practices should I consider with creating database indexes? How do I best select the feilds/combination of fields for a set of database indexes (rules of thumb)? Also, how do I best select which index to use as a clustered index? And when it comes to the access method, under what conditions should I use a btree over a hash or a gist or a gin (what are they anyway?).

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• Saving a huge dataset into SQL table in a XML column - MS SQL, C#.Net

  - by NLV

  Hello all I'm having a requirement where i've to save a dataset which has multiple tables in it in a sql table XML column by converting into an XML. The problem is that in some cases the dataset grows extremely huge and i get OutOfMemoryException. What i basically do is that i convert the dataset into an xml file and save it in the local disk and then load the XML again and send it as a stored procedure parameter. But when i write the dataset xml into the disk the file sizes over 700 Mb and when i load it in the XMLDocument object in memory i get OutOfMemoryException. How can get the dataset xml without saving it in a file and re-reading it again? Thank You NLV

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• Load a MySQL innodb database into memory

  - by jack

  I have a MySQL innodb database at 1.9GB, showed by following command. SELECT table_schema "Data Base Name", -> sum( data_length + index_length ) / 1024 / -> 1024 "Data Base Size in MB", -> sum( data_free )/ 1024 / 1024 "Free Space in MB" -> FROM information_schema.TABLES -> GROUP BY table_schema ; +--------------------+----------------------+------------------+ | Data Base Name | Data Base Size in MB | Free Space in MB | +--------------------+----------------------+------------------+ | database_name | 1959.73437500 | 31080.00000000 | My questions are: Does it mean if I set the innodb_buffer_pool_size to 2GB or larger, the whole database can be loaded into memory so much fewer read from disk requests are needed? What does the free space of 31GB mean? If the maximum RAM can be allocated to innodb_buffer_pool_size is 1GB, is it possible to specify which tables to loaded into memory while keep others always read from disk? Thanks in advance.

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• Weaknesses of Hibernate

  - by Sinuhe

  I would like to know which are the weak points of Hibernate 3. This is not pretended to be a thread against Hibernate. I think it will be a very useful knowledge for decide if Hibernate is the best option for a project or for estimating its time. A weakness can be: A bug Where JDBC or PLSQL are better Performance issues ... Also, can be useful to know some solutions for that problems, better ORM or techniques, or it will be corrected in Hibernate 4. For example, AFAIK, Hibernate will have a very bad performance updating 10000 rows comparing to JDBC in this query: update A set state=3 where state=2

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• pyopengl: Could it replace c++ ?

  - by Tom

  Hi everyone. I'm starting a computer graphics course, and I have to choose a language. Choices are between C++ and Python. I have no problem with C++, python is a work in progress. So i was thinking to go down the python road, using pyopengl for graphics part. I have heard though, that performance is an issue. Is python / pyopengl mature enough to challenge C++ on performance? I realize its a long shot, but I'd like to hear your thoughts, experiences on uses of pyopengl. Thanks in advance.

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• Temp file that exists only in RAM?

  - by Auraomega

  I'm trying to write an encrpytion using the OTP method. In keeping with the security theories I need the plain text documents to be stored only in memory and never ever written to a physical drive. The tmpnam command appears to be what I need, but from what I can see it saves the file on the disk and not the RAM. Using C++ is there any (platform independent) method that allows a file to exist only in RAM? I would like to avoid using a RAM disk method if possible. Thanks Edit: Thanks, its more just a learning thing for me, I'm new to encryption and just working through different methods, I don't actually plan on using many of them (esspecially OTP due to doubling the original file size because of the "pad"). If I'm totally honest, I'm a Linux user so ditching Windows wouldn't be too bad, I'm looking into using RAM disks for now as FUSE seems a bit overkill for a "learning" thing.

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• Push data to flex client

  - by KensoDev

  Howday, I want to push data to flex clients. I am talking about anywhere between 5000-15000 concurrent users, need to get data every time a currency is changed so that means lots of changes for lots of users. I have been looking into WebOrb.net, but the performance seem very poor (100 users concurrent) for a product so pricy (we purchased a license). So, I have to look into alternatives, I know there's fluorineFx but it seems no one is really using it for products and it lacks in examples and documentation. My question is: what products can answer my needs (.net backend) and what are the performance I can expect out of these products? Thanks

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• Best way to encrypt certain fiels in SQL Server 2008?

  - by Josh

  I'm writing a .net web app that will read and write information to a SQL 2008 backend database. Some of this information will be highly confidential in nature so I want to encrypt certain data elements. I dont want to use TDE or any full-database encryption for performance reasons. My main concern is protecting this sensitive data as a last resort against a SQL injection or even a database server compromise. My question is what is the best way to do this to preserve performance? Is it faster to use the SQL2008 encryption functions such as EncryptByKey, or would it be faster to encrypt and decrypt the data in the .NET web app itself using a symmetric key stored in the secure web.config and store the encrypted values in the DB?

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• Visual Artifacts in Visual Studio 2010

  - by Simon Chadwick

  I'm using VS 2010 on Windows Server 2003, running on a Dell Inspiron 9400 laptop. VS 2010 runs fine, except for persistent and random screen re-drawing issues. Samples of these are here. These artifacts occur as the mouse moves over items that highlight on a mouse-over event, while scrolling, and when switching tabs. VS 2008 has non of these issues, so I assume that it is related to VS 2010's use of WPF. Could it be that my video card or driver is not up to the task of rendering WPF? Some other WPF applications (not Silverlight) also have some of these screen repainting problems. I have tried a variety of settings in System Properties--Advanced--Performance Options--Visual Effects, and in the related "Advanced" tab, Processor Scheduling is adjusted for best performance of programs. Many thanks for any suggestions!

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• mdadm: Win7-install created a boot partition on one of my RAID6 drives. How to rebuild?

  - by EXIT_FAILURE

  My problem happened when I attempted to install Windows 7 on it's own SSD. The Linux OS I used which has knowledge of the software RAID system is on a SSD that I disconnected prior to the install. This was so that windows (or I) wouldn't inadvertently mess it up. However, and in retrospect, foolishly, I left the RAID disks connected, thinking that windows wouldn't be so ridiculous as to mess with a HDD that it sees as just unallocated space. Boy was I wrong! After copying over the installation files to the SSD (as expected and desired), it also created an ntfs partition on one of the RAID disks. Both unexpected and totally undesired! . I changed out the SSDs again, and booted up in linux. mdadm didn't seem to have any problem assembling the array as before, but if I tried to mount the array, I got the error message: mount: wrong fs type, bad option, bad superblock on /dev/md0, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so dmesg: EXT4-fs (md0): ext4_check_descriptors: Block bitmap for group 0 not in group (block 1318081259)! EXT4-fs (md0): group descriptors corrupted! I then used qparted to delete the newly created ntfs partition on /dev/sdd so that it matched the other three /dev/sd{b,c,e}, and requested a resync of my array with echo repair > /sys/block/md0/md/sync_action This took around 4 hours, and upon completion, dmesg reports: md: md0: requested-resync done. A bit brief after a 4-hour task, though I'm unsure as to where other log files exist (I also seem to have messed up my sendmail configuration). In any case: No change reported according to mdadm, everything checks out. mdadm -D /dev/md0 still reports: Version : 1.2 Creation Time : Wed May 23 22:18:45 2012 Raid Level : raid6 Array Size : 3907026848 (3726.03 GiB 4000.80 GB) Used Dev Size : 1953513424 (1863.02 GiB 2000.40 GB) Raid Devices : 4 Total Devices : 4 Persistence : Superblock is persistent Update Time : Mon May 26 12:41:58 2014 State : clean Active Devices : 4 Working Devices : 4 Failed Devices : 0 Spare Devices : 0 Layout : left-symmetric Chunk Size : 4K Name : okamilinkun:0 UUID : 0c97ebf3:098864d8:126f44e3:e4337102 Events : 423 Number Major Minor RaidDevice State 0 8 16 0 active sync /dev/sdb 1 8 32 1 active sync /dev/sdc 2 8 48 2 active sync /dev/sdd 3 8 64 3 active sync /dev/sde Trying to mount it still reports: mount: wrong fs type, bad option, bad superblock on /dev/md0, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so and dmesg: EXT4-fs (md0): ext4_check_descriptors: Block bitmap for group 0 not in group (block 1318081259)! EXT4-fs (md0): group descriptors corrupted! I'm a bit unsure where to proceed from here, and trying stuff "to see if it works" is a bit too risky for me. This is what I suggest I should attempt to do: Tell mdadm that /dev/sdd (the one that windows wrote into) isn't reliable anymore, pretend it is newly re-introduced to the array, and reconstruct its content based on the other three drives. I also could be totally wrong in my assumptions, that the creation of the ntfs partition on /dev/sdd and subsequent deletion has changed something that cannot be fixed this way. My question: Help, what should I do? If I should do what I suggested , how do I do that? From reading documentation, etc, I would think maybe: mdadm --manage /dev/md0 --set-faulty /dev/sdd mdadm --manage /dev/md0 --remove /dev/sdd mdadm --manage /dev/md0 --re-add /dev/sdd However, the documentation examples suggest /dev/sdd1, which seems strange to me, as there is no partition there as far as linux is concerned, just unallocated space. Maybe these commands won't work without. Maybe it makes sense to mirror the partition table of one of the other raid devices that weren't touched, before --re-add. Something like: sfdisk -d /dev/sdb | sfdisk /dev/sdd Bonus question: Why would the Windows 7 installation do something so st...potentially dangerous? Update I went ahead and marked /dev/sdd as faulty, and removed it (not physically) from the array: # mdadm --manage /dev/md0 --set-faulty /dev/sdd # mdadm --manage /dev/md0 --remove /dev/sdd However, attempting to --re-add was disallowed: # mdadm --manage /dev/md0 --re-add /dev/sdd mdadm: --re-add for /dev/sdd to /dev/md0 is not possible --add, was fine. # mdadm --manage /dev/md0 --add /dev/sdd mdadm -D /dev/md0 now reports the state as clean, degraded, recovering, and /dev/sdd as spare rebuilding. /proc/mdstat shows the recovery progress: md0 : active raid6 sdd[4] sdc[1] sde[3] sdb[0] 3907026848 blocks super 1.2 level 6, 4k chunk, algorithm 2 [4/3] [UU_U] [>....................] recovery = 2.1% (42887780/1953513424) finish=348.7min speed=91297K/sec nmon also shows expected output: ¦sdb 0% 87.3 0.0| > |¦ ¦sdc 71% 109.1 0.0|RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR > |¦ ¦sdd 40% 0.0 87.3|WWWWWWWWWWWWWWWWWWWW > |¦ ¦sde 0% 87.3 0.0|> || It looks good so far. Crossing my fingers for another five+ hours :) Update 2 The recovery of /dev/sdd finished, with dmesg output: [44972.599552] md: md0: recovery done. [44972.682811] RAID conf printout: [44972.682815] --- level:6 rd:4 wd:4 [44972.682817] disk 0, o:1, dev:sdb [44972.682819] disk 1, o:1, dev:sdc [44972.682820] disk 2, o:1, dev:sdd [44972.682821] disk 3, o:1, dev:sde Attempting mount /dev/md0 reports: mount: wrong fs type, bad option, bad superblock on /dev/md0, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so And on dmesg: [44984.159908] EXT4-fs (md0): ext4_check_descriptors: Block bitmap for group 0 not in group (block 1318081259)! [44984.159912] EXT4-fs (md0): group descriptors corrupted! I'm not sure what do do now. Suggestions? Output of dumpe2fs /dev/md0: dumpe2fs 1.42.8 (20-Jun-2013) Filesystem volume name: Atlas Last mounted on: /mnt/atlas Filesystem UUID: e7bfb6a4-c907-4aa0-9b55-9528817bfd70 Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Filesystem flags: signed_directory_hash Default mount options: user_xattr acl Filesystem state: clean Errors behavior: Continue Filesystem OS type: Linux Inode count: 244195328 Block count: 976756712 Reserved block count: 48837835 Free blocks: 92000180 Free inodes: 243414877 First block: 0 Block size: 4096 Fragment size: 4096 Reserved GDT blocks: 791 Blocks per group: 32768 Fragments per group: 32768 Inodes per group: 8192 Inode blocks per group: 512 RAID stripe width: 2 Flex block group size: 16 Filesystem created: Thu May 24 07:22:41 2012 Last mount time: Sun May 25 23:44:38 2014 Last write time: Sun May 25 23:46:42 2014 Mount count: 341 Maximum mount count: -1 Last checked: Thu May 24 07:22:41 2012 Check interval: 0 (<none>) Lifetime writes: 4357 GB 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: e177a374-0b90-4eaa-b78f-d734aae13051 Journal backup: inode blocks dumpe2fs: Corrupt extent header while reading journal super block

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