Thread: asynchronous commit feature

I'm testing the new asynch commit feature on various raid
configurations and my early findings is that it reduces the impact of
keeping wal and data on the same volume.  I have 10 disks to play
with, and am finding that it's faster to do a 10 drive raid 10 rather
than 8 drive raid 10 + two drive wal.

anybody curious about the results, feel free to drop a line.  I think
this will be a popular feature.

merlin

On Thu, Aug 23, 2007 at 09:09:00AM -0400, Merlin Moncure wrote:
> I'm testing the new asynch commit feature on various raid
> configurations and my early findings is that it reduces the impact of
> keeping wal and data on the same volume.  I have 10 disks to play
> with, and am finding that it's faster to do a 10 drive raid 10 rather
> than 8 drive raid 10 + two drive wal.
>
> anybody curious about the results, feel free to drop a line.  I think
> this will be a popular feature.

With or without a write cache on the RAID controller? I suspect that for
many systems, a write-caching controller will be very similar in
performance to async commit.
--
Decibel!, aka Jim Nasby                        decibel@decibel.org
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)

On 8/27/07, Decibel! <decibel@decibel.org> wrote:
> On Thu, Aug 23, 2007 at 09:09:00AM -0400, Merlin Moncure wrote:
> > I'm testing the new asynch commit feature on various raid
> > configurations and my early findings is that it reduces the impact of
> > keeping wal and data on the same volume.  I have 10 disks to play
> > with, and am finding that it's faster to do a 10 drive raid 10 rather
> > than 8 drive raid 10 + two drive wal.
> >
> > anybody curious about the results, feel free to drop a line.  I think
> > this will be a popular feature.
>
> With or without a write cache on the RAID controller? I suspect that for
> many systems, a write-caching controller will be very similar in
> performance to async commit.

I usually only work with mid to high end hardware.

The platform I'm testing on is:
10x146gb 15k rpm sas in Dell md1000
2xperc 5/e in active/active (5 drives each controller)
2x146gb 15krpm sas on the backplane perc 5/i (for o/s, wal)

in my experience, even with a high end raid controller moving the wal
offline is helpful in high activity systems, especially during
checkpoints.

merlin