Whit Armstrong wrote:
I have the opportunity to set up a new postgres server for our
production database. I've read several times in various postgres
lists about the importance of separating logs from the actual database
data to avoid disk contention.
Can someone suggest a typical partitioning scheme for a postgres server?
My initial thought was to create /var/lib/postgresql as a partition on
a separate set of disks.
However, I can see that the xlog files will be stored here as well:
http://www.postgresql.org/docs/8.3/interactive/storage-file-layout.html
Should the xlog files be stored on a separate partition to improve performance?
Any suggestions would be very helpful. Or if there is a document that
lays out some best practices for server setup, that would be great.
The database usage will be read heavy (financial data) with batch
writes occurring overnight and occassionally during the day.
server information:
Dell PowerEdge 2970, 8 core Opteron 2384
6 1TB hard drives with a PERC 6i
64GB of ram
We're running a similar configuration: PowerEdge 8 core, PERC 6i, but we have 8 of the 2.5" 10K 384GB disks.
When I asked the same question on this forum, I was advised to just put all 8 disks into a single RAID 10, and forget about separating things. The performance of a battery-backed PERC 6i (you did get a battery-backed cache, right?) with 8 disks is quite good.
In order to separate the logs, OS and data, I'd have to split off at least two of the 8 disks, leaving only six for the RAID 10 array. But then my xlogs would be on a single disk, which might not be safe. A more robust approach would be to split off four of the disks, put the OS on a RAID 1, the xlog on a RAID 1, and the database data on a 4-disk RAID 10. Now I've separated the data, but my primary partition has lost half its disks.
So, I took the advice, and just made one giant 8-disk RAID 10, and I'm very happy with it. It has everything: Postgres, OS and logs. But since the RAID array is 8 disks instead of 4, the net performance seems to quite good.
But ... your mileage may vary. My box has just one thing running on it: Postgres. There is almost no other disk activity to interfere with the file-system caching. If your server is going to have a bunch of other activity that generate a lot of non-Postgres disk activity, then this advice might not apply.
Craig
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