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Re: RAID 6 mdadm

Am Wednesday 10 April 2013 23:54:28 schrieb Stan Hoeppner:
> On 4/10/2013 12:32 PM, Dexter Filmore wrote:
> > Am Wednesday 10 April 2013 18:05:08 schrieb Ross Boylan:
> >>> You cannot get more than about 200MB/s out of a RAID1 setup, not even
> >>> with
> >>> 15krpm SAS drives. the RAID1 will never be faster than a single disk.
> >>> How
> >>> would it.
> >>
> >> It can read faster than a single disk by combining reads from different
> >> sectors on different disks.  I think your assertion is incorrect for
> >> reading, though  not for writing.
> >>
> >> Ross Boylan
> >
> > Then dm would have to manage/combine the reads from the involved disks.
> > I do not know better, but I doubt this is done.
> > I'll ask the raid list for curiousity's sake.
> It's not necessary to ask on linux-raid, and as you have not yet done
> so, I'll clarify this now:
> Both the md RAID1 and RAID10 personalities will read sectors in parallel
> from both disks in a mirror pair in most circumstances.  This has been
> the case for many years.  This is a read optimization only.  Writes
> occur in parallel as well, obviously, but as it's the same data the net
> data throughput isn't doubled, only the raw device throughput.  This
> should be obvious to anyone.  I'm merely being complete in my description.
> --
> Stan

Interesting. Only 1 and 10 or 5/6 as well?

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