[DRBD-user] DRBD and PostgreSQL - high load performance?

Philipp Reisner philipp.reisner at linbit.com
Tue Sep 13 11:22:49 CEST 2005

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Am Montag, 12. September 2005 17:09 schrieb Barry Price:
> Hi,
>
> We're looking at DRBD as a way to get a live-backup going on our database
> server.  It's an 8cpu SCSI-fired RAID1+0 monster with 16Gb RAM, and it's
> usually very, very busy.
>
> The database server is PostgreSQL 8, and consists of over 10,000 tables
> with up to 2,000 connections, processing several hundred queries per
> second.  DRBD looks like exactly what we need, but the testimonials I've
> seen have all been on rather smaller systems.
>
> Has anyone stress-tested DRBD on this level of system?  I'm concerned that
> even over gigabit, it simply won't be able to keep up with the speed of
> writes that we get over the SCSI controllers.  What happens when a backlog
> occurs?  Does the secondary machine simply queue the changes, or can it
> lock up?  Are there any other issues we should be concerned about?
>

Hi Barry,

Two of the more interesting clusters we run at Linbit

 PostgreSQL on a quad Opteron / 8 GB RAM Cluster
 Oracle on a quad HyperThreading enabled Xeons (=8 virtual CPUs) with
             8GB RAM Cluster.
 
Regarding Performance, look for the "Need for speed" subject in the
mailing list archives.

Ask your self: 
 Can my SCSI controllers / disks write more than 100MByte/second ?
 That is what GBit Ethernet delivers you.

If the secondary machine can not keep up with the writing speed
of the primary it will slow-down the primary in the end.

=> The machines should have about the same performance.

-Philipp
-- 
: Dipl-Ing Philipp Reisner                      Tel +43-1-8178292-50 :
: LINBIT Information Technologies GmbH          Fax +43-1-8178292-82 :
: Schönbrunnerstr 244, 1120 Vienna, Austria    http://www.linbit.com :



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