On Tue, 8 May 2007, Claus Guttesen wrote:
> In #postgresql on freenode, somebody ever mentioned that ZFS from
> Solaris
> helps a lot to the performance of pgsql, so dose anyone have information
> about that?
the filesystem you use will affect the performance of postgres
significantly. I've heard a lot of claims for ZFS, unfortunantly many of
them from people who have prooven that they didn't know what they were
talking about by the end of their first or second e-mails.
much of the hype for ZFS is it's volume management capabilities and admin
tools. Linux has most (if not all) of the volume management capabilities,
it just seperates them from the filesystems so that any filesystem can use
them, and as a result you use one tool to setup your RAID, one to setup
snapshots, and a third to format your filesystems where ZFS does this in
one userspace tool.
Even though those posters may have proven them selves wrong, zfs is
still a very handy fs and it should not be judged relative to these
statements.
I don't disagree with you, I'm just noteing that too many of the 'ZFS is
great' posts need to be discounted as a result (the same thing goes for
the 'reiserfs4 is great' posts)
once you seperate the volume management piece out, the actual performance
question is a lot harder to answer. there are a lot of people who say that
it's far faster then the alternate filesystems on Solaris, but I haven't
seen any good comparisons between it and Linux filesystems.
One could install pg on solaris 10 and format the data-area as ufs and
then as zfs and compare import- and query-times and other benchmarking
but comparing ufs/zfs to Linux-filesystems would also be a comparison
of those two os'es.
however, such a comparison is very legitimate, it doesn't really matter
which filesystem is better if the OS that it's tied to limits it so much
that the other one wins out with an inferior filesystem
currently ZFS is only available on Solaris, parts of it have been released
under GPLv2, but it doesn't look like enough of it to be ported to Linux
(enough was released for grub to be able to access it read-only, but not
the full filesystem). there are also patent concerns that are preventing
any porting to Linux.
on the other hand, it's integrated userspace tools are pushing people to
create similar tools for Linux (without needeing to combine the vairous
pieces in the kernel)
David Lang
---------------------------(end of broadcast)---------------------------
TIP 6: explain analyze is your friend
