[CentOS] question on RAID performance

[Ross S. W. Walker]

Jason wrote:
> John J. Lee wrote:
> > On Thu, Apr 10, 2008 at 8:18 PM, Miguel Medalha <miguelmedalha at sapo.pt> wrote:
> >>>
> >>> I was wonder what experiences there are out there with using RAID-X for
> >>> performance increases. I do use RAID-1 (2 disks) but am interested in
> >>> attemtps to gain higher R/W performance. Do the RAID-5's etc give
> >>> noticeable performace increases?
> >>
> >> Have you tried RAID 10? It combines the security of RAID 1 with the speed of
> >> RAID 0. dmraid supports this RAID type.
> >>
> >
> > I am currently running 7 raid10 data servers.  I can say read speed
> > increases but I doubt the write speed comparing to non raid setup.
> > The main advantage of the raid is redundancy but not
> > the performance.  If you want to boost the disk performance, go for
> > the faster drive with more than
> > 10,000rpm spinning speed.
> > 
> > -john
> > 
> 
> while it takes a minimum of 6 disks,  we've had great luck with RAID 50.
> Two separate RAID 5 arrays (fast read, moderate writes) that are then
> placed into a RAID 0 (fast read, fast write). you lose 2 drives worth of
> space, but lord it's fast and the data is mirrored.  Not sure if you can
> do the whole thing in software. I use two 3Ware 9650SE cards to do the
> RAID 5 and I do RAID 0 in software.

The choice of a RAID setup really depends on the application it is
used for and a RAID 50 or RAID 6 may be fast for a file server it
will perform poorly for a database, mail or virtual machine server.

If your application is database, mail or virtualization guests then
the way to go is RAID10.

The type of disk is important too. If you are doing file services
on RAID5/50/6 then you may as well stick with SATA, but if you
are doing database or mail then a SAS 10K drive may be in order
depending on the amount of transactions or virtual machines,
their type and applications they are running.

There is no one solution fits all unless you have the kind of money
to buy SAS 10K RAID10s on hardware RAID with BBU write cache for
everything.

Tell us what the application and hardware is, the number of clients,
VMs or transactions/mails you plan on it handling and a best-cost
solution can be provided.

BTW RAID50 can be done by adding 2 RAID5 PVs to a LVM VG and
creating striped LVs across them. All by software.

-Ross

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