Pierre C escribió:
On Tue, 09 Mar 2010 08:00:50 +0100, Greg Smith <greg@xxxxxxxxxxxxxxx>
wrote:
Scott Carey wrote:
For high sequential throughput, nothing is as optimized as XFS on
Linux yet. It has weaknesses elsewhere however.
When files are extended one page at a time (as postgres does)
fragmentation can be pretty high on some filesystems (ext3, but NTFS
is the absolute worst) if several files (indexes + table) grow
simultaneously. XFS has delayed allocation which really helps.
I'm curious what you feel those weaknesses are.
Handling lots of small files, especially deleting them, is really slow
on XFS.
Databases don't care about that.
There is also the dark side of delayed allocation : if your
application is broken, it will manifest itself very painfully. Since
XFS keeps a lot of unwritten stuff in the buffers, an app that doesn't
fsync correctly can lose lots of data if you don't have a UPS.
Fortunately, postgres handles fsync like it should be.
A word of advice though : a few years ago, we lost a few terabytes on
XFS (after that, restoring from backup was quite slow !) because a
faulty SCSI cable crashed the server, then crashed it again during
xfsrepair. So if you do xfsrepair on a suspicious system, please image
the disks first.
And then Which file system do you recommend for the PostgreSQL data
directory? I was seeying that ZFS brings very cool features for that.
The problem with ZFS is that this file system is only on Solaris,
OpenSolaris, FreeBSD and Mac OSX Server, and on Linux systems not What
do you think about that?
Regards
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