How To Move Your Linux Systems To ext4

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."

Comments

Not for the casual user

[halivar]

ext4fs is designed to be used in systems requiring many terabytes of storage and vast directory trees. It is unlikely the common desktop (or even, for that matter, the common server) will see appreciable performance increase with it.

Re:Not for the casual user

[Vellmont]

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.

Re:Not for the casual user

[Uncle Focker]

Disk sizes are going up. Since last year we've seen a terabyte on a single drive. Fix'd it for you.

Wikipedia entry

[drgould]

Link to Ext4 entry on Wikipedia for people who aren't familar with it (like me).

To all ext3 users...

[c0l0]

...who are on the lookout for a new fs to entrust with keeping their precious data: make sure to check out btrfs ( http://oss.oracle.com/projects/btrfs/ ). It's a really neatly spec'd filesystem (with all the zfsish stuff like data checksumming and so on), developed by Oracle employees under GPLv2, which will feature a converter application for ext3's on-disk-format - so you can migrate from ext3 to the much more feature-packed and modern btrfs without having to mkfs anew.

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.

undelete

[Nimey]

Oh, please. ext2 had "undelete" capability, just as it had filesystem compression capability. Neither were ever implemented.

Re:Wait, what?

[Waffle Iron]

They're probably using a 64-bit number to hold the timestamp. That gives you 1.8e19 discreet time intervals, so you're going to get ridiculous precision, dates ridiculously far into the future, or both. I assume that they went for precision because that arguably has more potential for use in the real world than worrying about files thousands of years into the future.

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.

What about comparison to other filesystems?

[Khopesh]

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 gets you started with a nice mapping of features. Second, a benchmarking of filesystems from 2006 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 (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.