Re: 10K vs 15k rpm for analytics - Mailing list pgsql-performance

Pierre C escribió:
> On Tue, 09 Mar 2010 08:00:50 +0100, Greg Smith <greg@2ndquadrant.com>
> 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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