How To Move Your Linux Systems To ext4 304
LinucksGirl writes "Ext4 is the latest in a long line of Linux file systems, and it's likely to be as important and popular as its predecessors. As a Linux system administrator, you should be aware of the advantages, disadvantages, and basic steps for migrating to ext4. This article explains when to adopt ext4, how to adapt traditional file system maintenance tool usage to ext4, and how to get the most out of the file system."
Not for the casual user (Score:5, Informative)
Wikipedia entry (Score:5, Informative)
To all ext3 users... (Score:5, Informative)
On a related sidenode: I'm very happy with SGI's xfs right now. ext\d isn't the only player in the field, so please, go out and boldly evaluate available alternatives. You won't be disappointed, I promise.
Re:Not for the casual user (Score:5, Informative)
It is unlikely the common desktop (or even, for that matter, the common server) will see appreciable performance increase with it.
Disk sizes are going up. In a few years you'll see a terabyte on a single drive. I'd also say that features like undelete, and online de-frag are important to anyone.
So while you may not see any real performance increases, that's really beside the point.
Step 1 (Score:3, Informative)
OK, all done!
undelete (Score:5, Informative)
Re:Not for the casual user (Score:5, Informative)
Re:Wait, what? (Score:5, Informative)
IIRC, today's PCs have high-resolution timers available that surpass the old 14.318MHz clock chip. If you can't get accurate nanoseconds out of the timers yet, they'll just round the numbers off. No big deal.
BTW, NTFS uses 100ns timestamp granularity, and it was designed when systems were almost 100X slower than today. So it had a similar amount of overkill, but that certainly doesn't seem to have had any negative impact on the acceptance of NTFS.
Re:But does it undelete... (Score:4, Informative)
POSIX was not and should not be designed in such a way that "undelete" is reliably possible. That's like saying can I unlight that match. Can I unbreak that egg?
An unreliable system that may, on the odd chance that the file structure has not changed too much, recover files from a disk that have not been over-written yet is no replacement for NOT being an idiot and being careful when you delete something.
Why bother? (Score:4, Informative)
What ever they do XFS and JFS will have way more testing and use than ext4 will ever have. I just don't get the point of ext4. It would be far more useful to fix the one remaining issue with XFS, the inability to shrink the filesystem none destructively, than to flog the dead horse which is ext2/3 even more with ext4, which is not one disk compatible anyway.
Re:Not for the casual user (Score:3, Informative)
And if you care about that data make a backup and even better run a raid.
Remember EVERY HARD DRIVE IS GOING TO FAIL SOMEDAY.
What about comparison to other filesystems? (Score:5, Informative)
Those features may be new to ext3, but not to the real competitors. I see nothing that might grant an edge over JFS or XFS. The real justifications will come from performance tests.
This reminds me of the recent NTFS article here, which actually suggested that since Hans Reiser is in jail and reiser4 is dead, we should consider NTFS. WTF? The ludicrousness of using NTFS as the primary filesystem is further justified in this article by its similar performance to ZFS, but both run in user-space (and are thus horrible in performance), so neither is really an option. What the heck is wrong with JFS and XFS?
Here are some real comparisons: First, Wikipedia's Comparison of file systems [wikipedia.org] gets you started with a nice mapping of features. Second, a benchmarking of filesystems from 2006 [linuxgazette.net] which is still quite applicable (though it doesn't yet cover ext4). What we need is a comparison of EXT4 to XFS and JFS (et al), with EXT2/3 in there for reference.
Recall that the biggest reason for using ext3 is that it is supported best of all the filesystems. If all hell breaks loose, even Tomsrtbt [toms.net] (an ancient rescue floppy pre-dating knoppix) can fix it. Ext4 breaks this backwards-compatibility to ext2. Therefore, I see no reason to use it. One might as well use something more stable and proven, especially while we lack numbers suggesting it performs as well or better.
Re:Not for the casual user (Score:2, Informative)
Re:But does it undelete... (Score:3, Informative)
Fifth, if you delete two files in different directories with the same name, both can't exist in the
Re:ext3 tops out at 16GB files? (Score:2, Informative)
"Block size Max file size Max filesystem size
1KiB 16GiB 2TiB
2KiB 256GiB 8TiB
4KiB 2TiB 16TiB
8KiB 2TiB 32TiB
It should be noted that the 8 KiB block size is only available on architectures which allow 8 KiB pages (such as Alpha)."
Ext4 still far from stable (Score:2, Informative)
Re:What about comparison to other filesystems? (Score:4, Informative)
Aside from the fact that no non-obsolete machine I've seen in the last few years has a disk drive, 'backwards compatibility with ext2' is a pretty lousy minimum requirement for a filesystem.
Heck, I can do recovery on Ext2/3, ReiserFS, JFS, XFS, and more using only a few-dozen-meg Debian netinstall image. I don't even want to know what an Ubuntu or Knoppix LiveCD could recover from.
OMFG. NTFS? (Score:2, Informative)
Re:Why bother? (Score:2, Informative)
Is Reiser4 really a dead project? (no pun intended) Seemed like it was just breaking some kernel coding standards but was working.
Would be a shame for the project to get scrapped. The performance numbers were great (faster and files were smaller.) ext4 is a LOT less interesting.
Re:Not for the casual user (Score:3, Informative)
man fsck
"filesystems on different drives will be checked at the same time to utilize parallelism available in the hardware."
If / is small it will be quicker. If / is a large partition then it hinders any parallelism.
The sixth field, (fs_passno), is used by the fsck(8) program to deter-
mine the order in which filesystem checks are done at reboot time. The
root filesystem should be specified with a fs_passno of 1, and other
filesystems should have a fs_passno of 2. Filesystems within a drive
will be checked sequentially, but filesystems on different drives will
be checked at the same time to utilize parallelism available in the
hardware. If the sixth field is not present or zero, a value of zero
is returned and fsck will assume that the filesystem does not need to
be checked.
Re:Not for the casual user (Score:4, Informative)
XFS has both extents and delayed allocation. I really don't know why we need Ext4. XFS has been a very solid fs for quite some time now, it's sad that more attention hasn't been payed to it from kernel hackers. The whole idea behind Ext4 seems to be more of a NIH syndrome than anything else. I could understand if it was radically different but it isn't.
Re:But does it undelete... (Score:3, Informative)
Sorry, but no way I'm gonna have a script that contains "sudo rm -rf" on my system...
Re:What about comparison to other filesystems? (Score:3, Informative)
Here's an Ext4/XFS/ZFS benchmark [brillig.org]
I would like to see a more recent benchmark that did include JFS/Reiser/etc, though.
Re:Not for the casual user (Score:3, Informative)
1) People wanting a lossless copy of the original media. i.e. purists.
2) Bonus content.
3) HD video.
4) Kids - they will want to watch different movies, over and over and over, at different ages.
5) Watching a movie with friends.
6) Keeping it all out of sight, out of mind.
7) Wanting to keep the NAS within a small power threshold, i.e. more easily done with higher storage density/fewer HDD. Better for the environment too with fewer HDD.
8) Never underestimate the bandwidth of a stationwagon full of HDD.
9) As someone else said, the packrat mentality. Who knows when that movie you want to watch will be out of production or perhaps banned?
Re:To all ext3 users... (Score:2, Informative)