On 10 March 2013 15:58, Greg Smith <greg@xxxxxxxxxxxxxxx> wrote:
On 3/1/13 6:43 AM, Niels Kristian Schjødt wrote:The Dell PERC H710 (actually a LSI controller) works fine for write-heavy workloads on a RAID 10, as long as you order it with a battery backup unit module. Someone must install the controller management utility and do three things however:
Hi, I'm going to setup a new server for my postgresql database, and I am considering one of these: http://www.hetzner.de/hosting/produkte_rootserver/poweredge-r720 with four SAS drives in a RAID 10 array. Has any of you any particular comments/pitfalls/etc. to mention on the setup? My application is very write heavy.
We're going to go with either HP or IBM (customer's preference, etc).
1) Make sure the battery-backup unit is working.
2) Configure the controller so that the *disk* write cache is off.
3) Set the controller cache to "write-back when battery is available". That will use the cache when it is safe to do so, and if not it will bypass it. That will make the server slow down if the battery fails, but it won't ever become unsafe at writing.
See http://wiki.postgresql.org/wiki/Reliable_Writes for more information about this topic. If you'd like some consulting help with making sure the server is working safely and as fast as it should be, 2ndQuadrant does offer a hardware benchmarking service to do that sort of thing: http://www.2ndquadrant.com/en/hardware-benchmarking/ I think we're even generating those reports in German now.
Thanks Greg. I will follow advice there, and also the one in your book. I do always make sure they order battery backed cache (or flash based, which seems to be what people use these days).
I think subject of using external help with setting things up did came up, but more around connection pooling subject then hardware itself (shortly, pgpool2 is crap, we will go with dns based solution and apps connection directly to nodes).
I will let my clients (doing this on a contract) know that there's an option to get you guys to help us. Mind you, this database is rather small in grand scheme of things (30-40GB). Just possibly a lot of occasional writes.
We wouldn't need German. But Proper English (i.e. british english) would always be nice ;)
Whilst on the hardware subject, someone mentioned throwing ssd into the mix. I.e. combining spinning HDs with SSD, apparently some raid cards can use small-ish (80GB+) SSDs as external caches. Any experiences with that ?
Thanks !
GJ
