On 11/26/2014 4:16 AM, Maila Fatticcioni wrote:
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On 11/25/2014 05:54 PM, Bill Moran wrote:
On Tue, 25 Nov 2014 17:27:18 +0100 Christoph Berg <cb@xxxxxxxx>
wrote:
Re: Bill Moran 2014-11-25
<20141125111630.d05d58a9eb083c7cf80ed9f8@xxxxxxxxxxxxxxxxx>
Anything with a journal is a performance problem. PostgreSQL
effectivly does its own journalling with the WAL logs. That's
not to say that there's no value to crash recovery to having a
journalling filesystem, but it's just to say that our
experience showed journaling filesystems to be slower. That
rules out ext4, unless you disable the journal. I seem to
remember ext4 with journalling disabled being one of the faster
filesystems, but I could be remembering wrong.
If you are using a non-journalling FS, you'll be waiting for a
full fsck after a system crash. Not sure that's an improvement.
It's an improvement if: a) You're investing in high-quality
hardware, so the chance of a system crash is very low. b) The
database is replicated, so your plan in the event of a primary
crash is to fail over to the backup anyway.
If both of those are in place (as they were at my previous job)
then the time it takes to fsck isn't an issue, and taking action
that causes the database to run faster when nothing is wrong can be
considered.
Obviously, the OP needs to assess the specific needs of the product
in question. Your point is very valid, and I'm glad you brought it
up (as a lot of people forget about it) but sometimes it's not the
most important factor.
Thank you a lot to have shared with me your experiences.
Indeed we will have two servers in cluster with high quality hardware
so a fsck restore shouldn't be a big problem.
I will analize the xfs option as well and then I will decide.
Thank you again,
Maila Fatticcioni
Also, if you do some timings, please share it with us, it'd be nice to
have some more data points.
-Andy
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