Which SCHED_ for DB server

Holger Kipp hk at alogis.com
Thu Sep 1 07:58:55 GMT 2005


On Thu, Sep 01, 2005 at 04:54:52PM +1000, Norberto Meijome wrote:
> I'm building a server that will run PostgreSQL with a database 
> containing several 10s of million records. The only things happening on 
> this box will be the SQL processes and other processes to parse raw data 
> and load into the DB. Users = a few connections via HTTP from an 
> intranet server (not more than 5 concurrently).

> I was wondering what is the best SCHED_ to set in the kernel.
> I currently have SCHED_4BSD but was wondering if _ULE would be better 
> for this
I would not care that much about the scheduler you want to use. In worst 
case, recompile the kernel and look at performance / userinteraction.

What looks worse (imho) is this:

> 4 x SATA 150 drives, 90% of it RAID5 with gvinum.

I do not know your applications, but if writing to disk is an issue:

- WAL-files should be written to physically separated disks.
- Write performance to RAID5 is not very good (tm).
  This is both with softraid and with hardware raid, although
  those raid controllers with 64MB or higher (+batterybackup)
  might increase the visible performance if only a few processes
  generate disk-i/o-load.
- ATA is not good for production - better use SCSI.

Best regards,
Holger Kipp

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