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EXT4 Is Coming
ah admin writes "A series of patches has been proposed in Linux kernel mailing list earlier by a team of engineers from Red Hat, ClusterFS, IBM and Bull to extend the Ext3 filesystem to add support for very large filesystems. After a long-winded discussion, the developers came forward with a plan to roll these changes into a new version — Ext4."
LWN had an interesting article on ext4 not long ago.
That post makes more sense if you realize that there should be ^ marks to show exponentiation, such as 10^51 and 2^140. Otherwise it just looks like gibberish numbers that someone made up and stuck in the wiki for shits and giggles.
Reiser4 does this.
Bogtha Bogtha Bogtha
Actually, XFS (SGI), JFS (IBM), and ZFS (Sun) are very well proven in the field, on their respective native operating systems. Given the situations they're used in (financial sector, pharmaceutical research data, supercomputing), they're far more proven that EXT(anything). Now, whether the average Linux user knows how to install, tune, and use them is a different issue, but if I were worried about scalable, mission-critical, filesystems, those three would be on the top of my list. (and my personal history says that while XFS never gave me any trouble, JFS would be my first choice. Nobody ever let me have a budget large enough to buy a machine that would justify ZFS).
With IBM's know-how in the mix, EXT4 may be able to join the above three, but it would seem to be time better spent fixing XFS/JFS support in Linux first, rather than worrying about backwards compatibility with EXT2.
the more accurate the calculations became, the more the concepts tended to vanish into thin air. R. S. Mulliken
Nobody has a fsck that can compare to e2fsck (ext2/ext3/etc.) for quality.
The e2fsck program has a huge test suite that it must pass before a release. A set of corrupted filesystems must be correctly repaired to be bit-for-bit identical to the desired result.
A typical fsck has a good chance of crashing (SIGSEGV, the "segmentation violation") when the going gets tough.
While FreeBSD's UFS developers were messing around with sync writes to avoid testing a fsck that would often crash, the ext2 developers ran full async and wrote a damn fine fsck to put things back in order. Now you can choose from three different levels of journalling, and you still get the ass-kicking fsck program.
There basically is no fsck for XFS, Reiserfs, or Reiser4. JFS doesn't have much AFAIK, and ZFS is a newborn.
What are you going to do when your fancy filesystem gets trashed? I hope you keep excellent backups, very recent and tested to be readable.
This is true, but let's look at the case of 1-2 drives:
Assuming we still want mirroring or volume management on our two drives:
The overhead is still greater for SVM or for linux md and sistina lvm. Both require more administration knowledge, time, and commands to accomplish the same tasks that ZFS can do in a couple commands. (Yes, I'm aware that mdadm helps the process a *bit*, but it's still obtuse.) Anyone who has setup either knows how annoying anything is with either choice. (having to micromanage partitions, etc.)
The biggest thing for ZFS in a ``small'' 1-2 drive usage case is, in my opinion, the pooling: ZFS doesn't require one to set volume sizes in advance. Since everything pulls out of a common pool, the size of volumes can grow or shrink accordingly. (Affected by free pool space or volume quotas.) So, that means that one can just create their volumes, and not have to worry about making them the wrong size.
I'd also argue that fault tolerance is important anywhere, large or small.
Another thing is on-disk, low overhead, compression that can be enabled just by toggling one filesystem paramater, live. For a lot of things that people store, this compression would save a lot of space.
They really put a lot of thought in ZFS. It scales amazingly well, from small to large. I'm not really giving it justice explaining it here, so I'd encourage you to look at the documentation with an open mind before just writing it off as an ``enterprise only'' thing.
dks
(I have no affiliation with Sun in any way.
What are you talking about? I said I didn't like the coding standards. I then had us change the code to conform to them.