On 21.06.2012 10:15, Wojciech Puchar wrote:
I do understand your setup but I dont have too agree that it is a
good
so i would repeat my question.
Assume you have 48 disks, in mirrored configuration (24 mirrors) and
480 users with their data on them.
Your solution with ZFS - ZFS crashes or you get double disk failure.
Assuming the latter by average one per 24 file (randomly chosen) is
destroyed which - in practice and limited time, means everything
destroyed. Actually more than one per 24 - large files can be spread
over.
Your solution with UFS - better as there is fsck which slowly but
successfully repairs problem. with double disk failure - the same!
You restore everything from backup (i assume you have one). This
takes like a day or more, one or two complete work days lost+all
users
in practice lost everything since last backup.
My solution with UFS - fsck in case of failure work in parallel on 24
disks so not that long. double disk failure means losing data of 1/24
users.
every one per 24 user cannot work, others work and i without any
stress do recover this 1/24 of users data from backup after putting
replacement disks.
1/24 of users lost data since last backup, and some hours of time.
Even assuming ZFS is perfect then we both have problems as often, but
my problems are 1/24 as severe as yours.
I think it is incorrect to assume that a failure with ZFS that cannot
be recovered could be recovered if you used UFS with fsck. What fsck
fixes in other file systems doesn't apply to ZFS by ZFS's design.
fsck deals with fixing superblock inconsistancies on non-journaled file
systems (like UFS/UFS2), not resurecting corrupted blocks on a disk.
http://www.c0t0d0s0.org/archives/6071-No,-ZFS-really-doesnt-need-a-fsck.html
http://en.wikipedia.org/wiki/Fsck
http://en.wikipedia.org/wiki/UFS2
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