Re: Linux Raid performance

[Learner Study <learner.study@gmail.com>]

Can you please throw light on what kind of bottlenecks that may impact perf....

Thanks!

On Sat, Apr 3, 2010 at 4:20 AM, Keld Simonsen <keld@keldix.com> wrote:
> 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
>> >> >> >
>> >> >> --
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