Re: Repository storage question (RAID)

You'll get more redundancy in the 8 disk solution for though you're
proportionately increasing the chance of drive failure across the set
you're reducing the volume of data exposed to a failure of two drives
in the same pair. So 8 drives gives more redundancy due to reduced
data per drive.

But don't quote me, I'm no statistician...

I wouldn't think the extra performance is going to produce a
significant improvement. Unless most of your files are large enough
to harness the transfer rate the varying seek times and controller
overhead will likely suck up the gains. This is all assuming you can
even compute and transmit the data to/from the client quickly enough
to get any improvement.

You're also probably near to saturating the IO channel even with 4 drives.

What kinds of infrastructure are other people running their Subversion
on and what are the stats of your repositories? It would be good to
get a feel for what kinds of use Subversion has been put to and on
what hardware.

EG. Extrapolating out our current CVS usage into what I expect for the
production subversion repository (when we get there) would be
something like:

  Legacy/unmigrated projects
  20,000 files, 3,500 folders, <500 commits per year.

  Main
  18,000 files, 5,500 folder, 8,000-10,000 commits per year.

3 teams of 10 devs each will hit the Main repository 99% of the time
and the 3 teams are rarely concurrent as we are spread around the
globe 6-8 hours apart each. One team is local (LAN) to the server.
High-latency, low bandwidth sucks big-time with CVS for the rest of
us...

CVS is currently on 4 disk RAID10 on a lowish spec dual CPU server box.

--
Talden
On 28/11/06, Thomas Harold <tgh@tgharold.com> wrote:
> Semi-off-topic / semi-on-topic...
>
> I'm getting ready to bulk out our storage for our repositories (and
> there's other stuff running in the background, but that happens during
> off-peak hours).
>
> Would it be better to go with a 4-disk RAID10 made up of 750GB SATA
> drives, or an 8-disk RAID10 made up of 320GB or 400GB SATA drives?  Do
> the extra spindles gain us enough to make the power increase worth it?
>
> (This would all be Software RAID in Linux 2.6 done on a PCIe box with
> plenty of I/O bandwidth.)
>
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