Linked by Thom Holwerda on Fri 1st Feb 2008 20:52 UTC, submitted by irbis
Linux "Ext4, being the successor to ext3, may well be the filesystem many of us are using a few years from now. Things have been relatively quiet on that front - at least, outside of the relevant mailing lists - but the ext4 developers have not been idle. Some of their work has now come to the surface with Ted Ts'o's posting of the ext4 merge plans for 2.6.25."
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RE: new features aren't impressing
by cjcox on Fri 1st Feb 2008 22:09 UTC in reply to "new features aren't impressing"
cjcox
Member since:
2006-12-21

uh... we've had those things in Linux for awhile. What are you talking about? Weird...

Reply Parent Score: 1

WereCatf Member since:
2006-02-15

uh... we've had those things in Linux for awhile. What are you talking about? Weird...

No, we don't. Name one single filesystem useable under Linux that does online self-healing? Or pooled storage? The LVM2 approach is not the same, and LVM2 is actually pretty cumbersome approach. F.ex. what do you do in the case where you have three hdds as a single LVM2 volume and one of the hdds is failing and you don't have a replacement available? With f.ex. ZFS you could just issue one command which removes the hdd from the pool, automatically moving the files to other spots in the pool. And the free snapshots? Nope, LVM2 doesn't provide that either. If you have all space reserved for your LVM2 volume then you can't take snapshots. You need to specifically leave space for them. Under a pooled storage model you don't need to reserve space. If there is space in the pool then you can take as many snapshots as needed without worrying about anything else, the amount of space needed is just reserved from the overall pool.

Reply Parent Score: 4

Wes Felter Member since:
2005-11-15

F.ex. what do you do in the case where you have three hdds as a single LVM2 volume and one of the hdds is failing and you don't have a replacement available? With f.ex. ZFS you could just issue one command which removes the hdd from the pool, automatically moving the files to other spots in the pool.


Actually, ZFS advertises this feature but they haven't gotten around to implementing it yet.

Reply Parent Score: 3

CrLf Member since:
2006-01-03

Under a pooled storage model you don't need to reserve space.


Then what's the point of having different filesystems? If space is one big pool shared by every filesystem, we just put everything under one big "/" and the effect is the same.

Reply Parent Score: 1

Kokopelli Member since:
2005-07-06

Name one single filesystem useable under Linux that does online self-healing? Or pooled storage? The LVM2 approach is not the same, and LVM2 is actually pretty cumbersome approach. F.ex. what do you do in the case where you have three hdds as a single LVM2 volume and one of the hdds is failing and you don't have a replacement available? With f.ex. ZFS you could just issue one command which removes the hdd from the pool, automatically moving the files to other spots in the pool. And the free snapshots? Nope, LVM2 doesn't provide that either.



I won't say that LVM2 is better than ZFS but you CAN issue a single command (pvmove) to migrate all extents from one physical volume to another. If you wanted to be cautious it would take two commands (one to freeze allocations on the failing physical volume, then another to move). I would like to point out, given your example, that it is NOT possible to remove a top level vdev such as an unmirrored disk in ZFS while it is a simple procedure to migrate the extents in LVM2. ;) ZFS has many features (RAIDz) that make this point sort of... pointless, but it was your example not mine.

That is not really what self-healing is about on ZFS though. The ability to self heal has more to do with the ability to have a fault tolerant system (usually a mirror) and recover the fault tolerance based on the internal checksums for the files to determine which copy was corrupted.

Personally I am comfortable with what LVM2 + filesystem choices gives me, even though they lack some very useful features that ZFS has. If zfs ever does make it into Linux (as a non FUSE FS) I am likely to migrate to it.

Reply Parent Score: 2