Re: Linux Raid performance

[Keld Simonsen <keld@keldix.com>]

On Fri, Apr 02, 2010 at 02:37:40PM -0700, Learner Study wrote:
> I have seen ~180MB/s RAID5 performance with 4 disks...are you saying
> that I could achieve even higher if I have more number of disks (so
> instead of 3+1, try 6+1 or 9+1)?
> Logically, this sounds right but wanted to verify my thought process
> with you....

Yes, with more spindles you can generally expect more performance.
Beware of bottlenecks, tho.

Best regards
keld

> Thanks!
> 
> On Fri, Apr 2, 2010 at 2:14 PM, Keld Simonsen <keld@keldix.com> wrote:
> > On Fri, Apr 02, 2010 at 10:55:53AM -0700, Learner Study wrote:
> >> Hi Keld:
> >>
> >> Thanks for your email...
> >>
> >> 1. Can you pls point me to this benchmark (which shows 500MB/s)? I
> >> would like to know which CPU, HDDs and kernel version used to achieve
> >> this...
> >
> > http://home.comcast.net/~jpiszcz/20080329-raid/
> > 496843   KB/s for sequential input with 10 raptor drives
> > There probably is an email in the archives with more info on the
> > test.
> >
> >> 2. Secondly, I would like to understand how raid stack (md driver)
> >> scales as we add more cores...if single core gives ~500MB/s, can two
> >> core give ~1000MB/s? can four cores give ~2000MB/s? etc....
> >
> > No, the performance is normally limited by the number of drives.
> > I would not wsay that more cores woould do a little
> > but it would be in the order of 1-2 % I think.
> > This is also dependent on wheteher the code actually runs threaded.
> > I doubt it....
> >
> > best regard
> > keld
> >
> >>
> >> Thanks for your time.
> >>
> >> On Fri, Apr 2, 2010 at 4:05 AM, Keld Simonsen <keld@keldix.com> wrote:
> >> > On Thu, Apr 01, 2010 at 08:07:25PM -0700, Learner Study wrote:
> >> >> Hi Keld:
> >> >>
> >> >> Do we have raid5/6 numbers for linux on any multi-core CPU? Most of
> >> >> the benchmarks I have seen on wiki show raid5 perf to be ~150MB/s with
> >> >> single core CPUs. How does that scale with multiple cores? Something
> >> >> like intel's jasper forest???
> >> >
> >> > I have not checked if the benchmarks were on multi core machines.
> >> > It should not matter much if there were more than one CPU, but
> >> > of cause it helps a little. bonnie++ test reports cpu usage, and this
> >> > is not insignificant, say in the 20 -60 % range for some tests,
> >> > but nowhere near a bottleneck. There was one with a raid5 performance
> >> > seq read of about 500 MB/s with 36 % cpu utilization, so it is
> >> > definitely possible to come beyound 150 MB/s. The speed is largely
> >> > dependent on number of disk drives you employ.
> >> >
> >> >
> >> >> If available, can u pls point me to numbers with multi-core CPU?
> >> >
> >> > I dont have such benchmarks AFAIK. But new benchmarks are always welcome,
> >> > so please feel free to submit your findings.
> >> >
> >> > Best regards
> >> > keld
> >> >
> >> >> Thanks!
> >> >>
> >> >> On Wed, Mar 31, 2010 at 1:15 PM, Keld Simonsen <keld@keldix.com> wrote:
> >> >> > On Wed, Mar 31, 2010 at 12:42:57PM -0700, Learner Study wrote:
> >> >> >> Hi Linux Raid Experts:
> >> >> >>
> >> >> >> I was looking at following wiki on raid perf on linux:
> >> >> >>
> >> >> >> https://raid.wiki.kernel.org/index.php/Performance
> >> >> >>
> >> >> >> and notice that the performance numbers are with 2.6.12 kernel.
> >> >> >>
> >> >> >> Do we perf numbers for:
> >> >> >> - latest kernel (something like 2.6.27 / 2.6.31)
> >> >> >> - raid 5 and 6
> >> >> >>
> >> >> >> Can someone please point me to appropriate link?
> >> >> >
> >> >> > The link mentioned above has a number of other performance reports, for other levels of the kernel.
> >> >> > Anyway you should be able to get comparable results for newer kernels, the kernel has not become
> >> >> > slower since 2.6.12 on RAID.
> >> >> >
> >> >> > best regards
> >> >> > Keld
> >> >> >
> >> >> --
> >> >> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> >> >> the body of a message to majordomo@vger.kernel.org
> >> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >> >
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html