[PERFORM] Tablespaces on a raid configuration

2012-03-30 Thread Campbell, Lance
PostgreSQL 9.0.x When PostgreSQL storage is using a relatively large raid 5 or 6 array is there any value in having your tables distributed across multiple tablespaces if those tablespaces will exists on the same raid array? I understand the value if you were to have the tablespaces on differ

Re: [PERFORM] Tablespaces on a raid configuration

2012-03-30 Thread k...@rice.edu
On Fri, Mar 30, 2012 at 02:45:36PM +, Campbell, Lance wrote: > PostgreSQL 9.0.x > When PostgreSQL storage is using a relatively large raid 5 or 6 array is > there any value in having your tables distributed across multiple tablespaces > if those tablespaces will exists on the same raid arra

Re: [PERFORM] Tablespaces on a raid configuration

2012-03-30 Thread Greg Spiegelberg
On Fri, Mar 30, 2012 at 8:45 AM, Campbell, Lance wrote: > PostgreSQL 9.0.x > > When PostgreSQL storage is using a relatively large raid 5 or 6 array is > there any value in having your tables distributed across multiple > tablespaces if those tablespaces will exists on the same raid array?

Re: [PERFORM] Tablespaces on a raid configuration

2012-03-30 Thread Andrew Dunstan
On 03/30/2012 10:45 AM, Campbell, Lance wrote: PostgreSQL 9.0.x When PostgreSQL storage is using a relatively large raid 5 or 6 array is there any value in having your tables distributed across multiple tablespaces if those tablespaces will exists on the same raid array? I understand th

Re: [PERFORM] Tablespaces on a raid configuration

2012-03-30 Thread Merlin Moncure
On Fri, Mar 30, 2012 at 10:02 AM, Andrew Dunstan wrote: > Not answering your question, but standard advice is not to use RAID 5 or 6, > but RAID 10 for databases. Not sure if that still hold if you're using SSDs. Yeah, for SSD the equations may change. Parity based RAID has two problems: perform

Re: [PERFORM] Tablespaces on a raid configuration

2012-03-30 Thread Craig James
On Fri, Mar 30, 2012 at 7:53 AM, k...@rice.edu wrote: > On Fri, Mar 30, 2012 at 02:45:36PM +, Campbell, Lance wrote: >> PostgreSQL 9.0.x >> When PostgreSQL  storage is using a relatively large raid  5 or 6 array is >> there any value in having your tables distributed across multiple >> table

Re: [PERFORM] Linux machine aggressively clearing cache

2012-03-30 Thread Josh Berkus
>> Read cache of course does not need to be flushed and can simply be >> dumped when the memory is needed, and so Linux will keep more or >> less unlimited amounts of read cache until it needs the memory for >> something else > > Right, that's the normal behavior. Except not on this machine

Re: [PERFORM] database slowdown while a lot of inserts occur

2012-03-30 Thread Tomas Vondra
On 29.3.2012 21:27, Bob Lunney wrote: > Lance, > > May small inserts cause frequent fsyncs. Is there any way those small > inserts can be batched into some larger sets of inserts that use copy to > perform the load? Not necessarily - fsync happens at COMMIT time, not when the INSERT is performed

Re: [PERFORM] database slowdown while a lot of inserts occur

2012-03-30 Thread Tomas Vondra
Hi, On 29.3.2012 19:59, Campbell, Lance wrote: > PostgreSQL 9.0.x > > We have around ten different applications that use the same database. > When one particular application is active it does an enormous number of > inserts. Each insert is very small. During this time the database > seems to s

Re: [PERFORM] Tablespaces on a raid configuration

2012-03-30 Thread Tomas Vondra
On 30.3.2012 16:53, k...@rice.edu wrote: > On Fri, Mar 30, 2012 at 02:45:36PM +, Campbell, Lance wrote: >> PostgreSQL 9.0.x >> When PostgreSQL storage is using a relatively large raid 5 or 6 array is >> there any value in having your tables distributed across multiple >> tablespaces if thos