Talk:Ext4

Premature?

I'm not sure this article is appropriate as yet, since I don't think that it's gone past the proposal stage. Not sure if it should be deleted though. FrozenPurpleCube 16:42, 1 July 2006 (UTC)

At some point in the future we should have a page about ext4. However it is too early right now. So I've changed it to a redirect. If we did put it up for deletion and it was deleted, someone would just come along and replace it. So, IMHO, a redirect is good enough for now. AlistairMcMillan 19:01, 1 July 2006 (UTC)

: Sorry I didn't read the discussion before re-creating the article. But I'll let it stay there if you want to remove it any way.

Travis| 2:22, 1 August 2006 (PST)

Yeah, considering that the page you linked to is from 1997, I don't think it's a valid inclusion anyway. Maybe in terms of historical perspective, if there is actually an EXT4 added to the Linux Source Tree. Until then, the redirect is best. FrozenPurpleCube 04:31, 2 August 2006 (UTC)

--- Topic for #linuxfs is Link to file system bugzilla entries now on http://linuxfs.pbwiki.com/ || Some cool bugs there, check 'em out || Linus merged ext4 — Preceding unsigned comment added by 68.33.112.13 (talk • contribs) 12 October 2006 (UTC)

OS's?

Is it sure ext4 works on BSD and Mac OS X? I seriously doubt that. Can anyone bring more clarity to this matter, so we can remove those OS's if needed? Ludootje 10:23, 11 October 2006 (UTC)

If ext3 works, then parts of ext4 may work. But when using stuff like extents, you first need to add support for that to the BSD/OSX kernels. Read the paragraph about backward/forward compatibility. -Jen 15:46, 19 October 2006 (UTC)

HTrees

The HTrees discussed are not explained sufficiently - the explanation needs to be extended or a new Wiki article needs to be created for "HTrees". Doronyg (talk) 14:30, 14 January 2008 (UTC)

It should probably be a page in itself since ext3 also uses htrees

Narayannewton (talk) 18:26, 14 January 2008 (UTC)

Table

Is the table data structure a Hash Table? If it is it should have link to it. 213.205.69.57 (talk) 18:52, 28 February 2008 (UTC)

defragmentation

Issue with the online defragmentation section: The section below is just pure rubbish.

Online defragmentation Ext4 will also have an online defragmenter. Even with the various techniques used to avoid it, a long lived file system does tend to become fragmented over time. Ext4 has a tool which can defragment individual files or entire file systems."

Here is my note to explain why this section must be corrected. NOTE: Come on! That is a total lie! Ext4 does NOT have a tool to defragment individual tools or entire filesystems! it just doesnt! If it does, I challenge the author of this unsupported statement to back up this claim with some information. What is this tool called? Where can I get it? Is is a production ready tool, or is it a kludged hack written to do some quick benchmarks/testing for an academic paper that was written early in 2007 and which has had little or no follow-up or adoption by users since then? There are 3rd party tools such as Shake which can be used to defrag any filesystem, including ext4, but they do so very inefficiently. Moving data off a partition, then back also defragments, but we don't say a filesystem has a defragmenter just because the standard unix commands mv or tar can be used to move data off then back onto the partition. Keep this discussion of Ext4 honest, or this wikipedia entry is worthless. The statement "Ext4 will also have an online defragmenter" is also a statement of hope and faith, and at this time is pure fantasy. Ext3 never got an online or offline defragmenter. How can anyone be 100% sure that ext4 will get one? Be honest. Admit that ext4 has no online or offline defragmenter. Feel free to state that an online defragmenter MAY be available in the future. That is all we can say at the moment.

I suggest the misleading statement on defragmentation be changed to something like the following:

Vague Promises of future Online defragmentation Ext4 may in future provide an online defragmenter. Even with the various techniques used to avoid it, a long lived file system does tend to become fragmented over time. Ext4 currently has no tool which can defragment individual files or entire file systems.

PS - if anyone thinks this defragmentation issue can continue to be glossed over by statements like those currently in this wiki page, they are mistaken. Defragmentation has been an appalling performance killer on ext3 and other filesystems for many years, and allowing untrue statements and vague promises from developers to gloss over these problems cannot be allowed anymore! Don't let them get away with it. Until these guys produce a proper online defragmenter - we should let it be known that the lack of one is a problem! If the true situation is actually publicised, and made clearly visible in wiki pages such as these, perhaps these developers will realise they have to actually produce a defragmenter BEFORE they can brag about having done so.

THANK YOU, on behalf of all linux users everywhere who have been putting up with fragged filesystems for years, because those in the know have refused to admit what a performance killer it is - and they've been reluctant to do that because the developers have never provided a solution, and so, to admit the standard linux filesystems are crippled by fragmentation is too embarrassing for linux lovers and can't be allowed...

—Preceding unsigned comment added by 61.88.61.66 (talk) 02:03, 27 March 2008 (UTC)

Please see here. An online defragmenter already exists, it just isn't merged yet. And that's not counting the ability to treat ext4 filesystems as ext2 (depending on options) and use ext2 defragmenters on it. --Yamla (talk) 14:34, 27 March 2008 (UTC)

Also, I'd like to see a reliable source that indicates lack of online defragmentation in ext3 is a performance killer. I've been using ext3 in production environments for years and have not seen this performance issue on any system. Still, I'm not a reliable source. A simple link will suffice, no need to engage in inappropriate discussion about it here. --Yamla (talk) 14:36, 27 March 2008 (UTC)

Just to follow up, if anyone is trying to use this discussion as a reliable source (not a good idea), this page (5.10.11) indicates that it is probably not a good idea to use the ext2 defrag program even on an ext2 filesystem. However, it also indicates that fragmentation is really not a problem on Linux file systems. Other references I've found indicate that this may be a problem if your file system is over 90% of 95% full. --Yamla (talk) 21:32, 30 March 2008 (UTC)

Once again, we're told an online defragmenter exists, but... oh wait... its not available! Once again someone mentions the the ext2 defrag tool that has been obsolete and DANGEROUS for years. Noone in their right mind would use ext2defrag on an ext2 filesystem, let-alone on ext3 or ext4. Once again someone says that fragmentation is not an issue, just because they havent noticed it. How do you know its not an issue? Just because your production linux servers perform adequately, does not mean they couldn't perform better. Take one of your production filesystems and run a proper benchmark on it. Then copy all data off it, delete everything on it, copy data back, redo benchmark, be amazed. Saying it is not an issue is head-in-the-sand nonsense. Also, probably, what is occurring is that you have smart SCSI controllers which are letting your drives do out of order reads on all the fragments, reading them in the fastest way that they'll come off disk, and reassembling them in controller. That will mitigate the problem somewhat. Try using non-scsi controllers, ie an IDE or simple SATA drive - and you will be horrified - you will easily lose 50% or more of your disk speed due to fragmentation, and it doesnt take long, and you DONT have to run your drives to 95% full for it to happen - though, of course it will accelerate the fragging process if you do. —Preceding unsigned comment added by 61.88.61.66 (talk) 05:51, 1 April 2008 (UTC)

This is not a discussion forum. Please see WP:NOT. --Yamla (talk) 15:41, 1 April 2008 (UTC)

errrr... there are three little tabs at the top of this Ext4 wiki page. In case you havent noticed... this IS the "discussion" tab... —Preceding unsigned comment added by 61.88.61.66 (talk) 23:48, 1 April 2008 (UTC)

I am just flabbergasted at the complete denial that everyone lives in w.r.t defragmentation. Yamla, you seem like a nice guy, i'm not trying to give you a hard time - but you said above that your link to tldp "indicates that it is probably not a good idea to use the ext2 defrag program even on an ext2 filesystem." But no, that is NOT what the tldp page indicated. What it actually said was: "However, it is HIGHLY recommended that you NOT use it. It was designed for and older version of ext2, and has not been updated since 1998! I only mention it here for references purposes." That means it would be sheer, utter, suicide to use that defragger. Don't gloss over that by saying oh its probably not a good idea to use it. No. Its worse than that. The simple fact is it just CANT be used ever by any sane person. A refernce to linux symposium nearly a year ago in June 2007 does not give ext4 an online defragger.

Why can't people just write a half-decent defragger for a modern linux filesystem! It doesnt have to be ultra-super-dooper-efficient. Just 100% safe, effective, and, reasonably efficient. Thats all. It's not asking too much. I don't like to seem ungrateful to open source software developers, i reckon they're great etc, I just wish they would stop trying to get me to swallow this sweetly coated poison pill, year after year. You will have a defragger they say. rrrgh. Ok for God/Allah's sake just produce said defragger so i can say "thank you thank you" and be happy, instead of being a sourpuss. —Preceding unsigned comment added by 61.88.61.66 (talk) 00:17, 2 April 2008 (UTC)

This is not a general discussion forum for ext4. I have now semi-protected this page so that anonymous user, 61.88.61.66, can read this, which explains this in more detail. --Yamla (talk) 00:21, 2 April 2008 (UTC)

If anyone cares to check, the source is available for a work in progress version of the defragger available at [ hhttp://www.kernel.org/pub/linux/kernel/people/tytso/ext4-patches/LATEST/broken-out/ext4-online-defrag-command.patch] , it is compilable if you commend out the comments and rename it to a .c file —Preceding unsigned comment added by 216.248.103.177 (talk) 16:56, 16 July 2008 (UTC)

EXT4 will have a mutiblock allocator which will reduce fragmentation since ext4 will know ahead of time the file size only if delayed allocation is on--24.128.74.11 (talk) 04:06, 16 July 2008 (UTC)

Bad jokes and other deleted nonsense?

I love how the article says that "H trees are higher alphabetically than B* trees", then points a citation to the Wikipedia article on Alphabetical order!

Comedic gold!--Dwedit (talk) 12:01, 20 June 2008 (UTC)

Creation date timestamps?

Could someone add a citation on whether ext4 will support creation date timestamps for files? I haven't found any information on this feature anywhere on the Internet and only this article on Wikipedia suggests that ext4 will support creation date timestamps leading me to believe that this is just wishful thinking. I believe we should delete this section in order to not create wrong expectations on ext4.