On Sun, Nov 28, 2010 at 11:41:35PM -0600, Stan Hoeppner wrote:
> Yclept Nemo put forth on 11/28/2010 9:57 PM:
> > You mention an eight-core machine (8c?). Since I operate a dual-core
> > system, would it make sense to increase my AG count slightly, to five
> > or six?
> Dave didn't mention the disk configuration of his "workstation". I'm
> guessing he's got a local RAID setup with 8-16 drives.
2 SSDs in RAID0.
> AG count has a
> direct relationship to the storage hardware, not the number of CPUs
> (cores) in the system.
Actually, I used 16 AGs because it's twice the number of CPU cores
and I want to make sure that CPU parallel workloads (e.g. make -j 8)
don't serialise on AG locks during allocation. IOWs, I laid it out
that way precisely because of the number of CPUs in the system...
And to point out the not-so-obvious, this is the _default layout_
that mkfs.xfs in the debian squeeze installer came up with. IOWs,
mkfs.xfs did exactly what I wanted without me having to tweak
> If you have a 24 core system (2x Magny Cours)
> and a single disk, creating an FS with 24 AGs will give you nothing, and
> may actually impede performance due to all the extra head seeking across
> those 24 AGs.
In that case, you are right. Single spindle SRDs go backwards in
performance pretty quickly once you go over 4 AGs...