On Tue, 8 May 2007, david@xxxxxxx wrote:
one issue with journaling filesystems, if you journal the data as well as the
metadata you end up with a very reliable setup, however it means that all
your data needs to be written twice, oncce to the journal, and once to the
final location. the write to the journal can be slightly faster then a normal
write to the final location (the journal is a sequential write to an existing
file), however the need to write twice can effectivly cut your disk I/O
bandwidth in half when doing heavy writes. worse, when you end up writing mor
ethen will fit in the journal (128M is the max for ext3) the entire system
then needs to stall while the journal gets cleared to make space for the
additional writes.
if you don't journal your data then you avoid the problems above, but in a
crash you may find that you lost data, even though the filesystem is 'intact'
according to fsck.
That sounds like an ad for FreeBSD and UFS2+Softupdates. :)
Metadata is as safe as it is in a journaling filesystem, but none of the
overhead of journaling.
Charles
David Lang
Steve Atkins wrote:
On May 7, 2007, at 2:55 PM, David Levy wrote:
> Hi,
> > I am about to order a new server for my Postgres cluster. I will
> probably get a Dual Xeon Quad Core instead of my current Dual Xeon.
> Which OS would you recommend to optimize Postgres behaviour (i/o
> access, multithreading, etc) ?
> > I am hesitating between Fedora Core 6, CentOS and Debian. Can anyone
> help with this ?
Well, all three you mention are much the same, just with a different
badge on the box, as far as performance is concerned. They're all
going to be a moderately recent Linux kernel, with your choice
of filesystems, so any choice between them is going to be driven
more by available staff and support or personal preference.
I'd probably go CentOS 5 over Fedora just because Fedora doesn't
get supported for very long - more of an issue with a dedicated
database box with a long lifespan than your typical desktop or
interchangeable webserver.
I might also look at Solaris 10, though. I've yet to play with it much,
but it
seems nice, and I suspect it might manage 8 cores better than current
Linux setups.
Cheers,
Steve
---------------------------(end of broadcast)---------------------------
TIP 5: don't forget to increase your free space map settings
Regards
Ian
---------------------------(end of broadcast)---------------------------
TIP 3: Have you checked our extensive FAQ?
http://www.postgresql.org/docs/faq
---------------------------(end of broadcast)---------------------------
TIP 1: if posting/reading through Usenet, please send an appropriate
subscribe-nomail command to majordomo@xxxxxxxxxxxxxx so that your
message can get through to the mailing list cleanly
