Hi,
I configured a similar architecture some months ago and this is the best choice after some pgbench and Bonnie++ tests.
Server: DELL R720d
CPU: dual Xeon 8-core
RAM: 32GB ECC
Controller PERC H710
Disks:
2xSSD (MLC) Raid1 for Operating System (CentOS 6.4)
4xSSD (SLC) Raid10 for WAL archive and a dedicated "fast tablespace", where we have most UPDATE actions (+ Hot spare).
10xHDD 15kRPM Raid5 for "default tablespace" (optimized for space, instead of Raid10) (+ Hot spare).
Our application have above 200 UPDATE /sec. (on the "fast tablespace") and above 15GB per die of records (on the "default tablespace").
After the testing phase I had the following conclusion:
4xSSD (SLC) RAID 10 vs. 10xHDD RAID 5 have comparable I/O performance in the sequential Read and Write, but much more performance on the Random scan (obviously!!), BUT as far I know the postgresql I/O processes are not heavily involved in a random I/O, so at same price I will prefer to buy 10xHDD instead of 4xSSD (SLC) using above 10x of available space at the same price!!
10xHDD RAID 10 vs. 10xHDD RAID 5 : with Bonnie++ I noticed a very small difference in I/O performance so I decided to use RAID 5 + a dedicated Hot Spare instead of a RAID10.
If I could go back, I would have spent the money of the SLC in other HDDs.
regards.
2014-02-17 16:03 GMT+01:00 Niels Kristian Schjødt <nielskristian@xxxxxxxxxxxxx>:
Hi,Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx)
I’m kind of a noob when it comes to setting up RAID controllers and tweaking them so I need some advice here.
I’m just about to setup my newly rented DELL R720 12. gen server. It’s running a single Intel Xeon E5-2620 v.2 processor and 64GB ECC ram. I have installed 8 300GB SSDs in it. It has an PERC H710 raid controller (Based on the LSI SAS 2208 dual core ROC).
Now my database should be optimized for writing. UPDATEs are by far my biggest bottleneck.
Firstly: Should I just put all 8 drives in one single RAID 10 array, or would it be better to have the 6 of them in one RAID 10 array, and then the remaining two in a separate RAID 1 array e.g. for having WAL log dir on it’s own drives?
Secondly: Now what settings should I pay attention to when setting this up, if I wan’t it to have optimal write performance (cache behavior, write back etc.)?
THANKS!
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