Re: [PERFORM] Optimal settings for RAID controller - optimized for writes

[DFE]

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 <
nielskrist...@autouncle.com>:

> Hi,
>
> 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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Re: [PERFORM] Specifications for a new server

[DFE]

I can suggest to have a disks' layout using at least two RAIDs:

1) RAID10 SSD (or 15kRPM HDD) SAS for O.S. and "pg_xlog" folder where PG
writes WAL files before checkpoint calls.
2) RAID10 using how many span is possible for the default DB folder.


Regards,


2014-05-06 11:13 GMT+02:00 Johann Spies :

> I am busy reading Gregory Smith' s  PostgreSQL 9.0 High Performance and
> when the book was written he seemed to me a bit sceptical about SSD's.  I
> suspect the reliability of the SSD's has improved significantly since then.
>
> Our present server (128Gb RAM and 2.5 Tb disk space  and 12 CPU cores -
> RAID 10) will become a development server and we are going to buy a new
> server.
>
> At the moment the 'base'  directory uses 1.5Tb  of disk space and there is
> still more data to come.
>
> The database contains blbliometric data that receive updates on a weekly
> basis but not much changes other than that except for cleaning of data by a
> few persons.
>
> Some of the queries can take many hours to finish.
>
> On our present system there are sometimes more than 300GB in temporary
> files which I suspect will not be the case on the new system with a much
> larger RAM.
>
> Analysis or the SAR-logs showed that there were too much iowait in the
> CPU's on the old system which has a lower spec CPU than the ones considered
> for the new system.
>
> We are looking possibly the following hardware:
>
> CPU: 2 x  Ivy Bridge 8C E5-2667V2 3.3G 25M 8GT/s QPI - 16 cores
> RAM: 24 x 32GB DDR3-1866 2Rx4 LP ECC REG RoHS  - 768Gb
>
> with enough disk space - about 4.8 Tb on RAID 10.
> My question is about the possible advantage and usage of SSD disks in the
> new server.  At the moment I am considering using 2 x 200GB SSD' s for a
> separate partion for temporary files and 2 x 100GB for the operating system.
>
> So my questions:
>
> 1. Will the SSD's in this case be worth the cost?
> 2.  What will the best way to utilize them in the system?
>
> Regards
> Johann
> --
> Because experiencing your loyal love is better than life itself,
> my lips will praise you.  (Psalm 63:3)
>