* RAID 5 parity layout left-symmetric vs right symmetric vs other choices
@ 2011-02-02 23:27 Budai Laszlo
2011-02-07 17:41 ` Beolach
0 siblings, 1 reply; 2+ messages in thread
From: Budai Laszlo @ 2011-02-02 23:27 UTC (permalink / raw)
To: linux-raid
Hello everybody,
can someone direct me to some documentation describing the pros and cons
for choosing a certain layout.
Any explanation on this topic is welcome.
Kind regards,
Laszlo Budai
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: RAID 5 parity layout left-symmetric vs right symmetric vs other choices
2011-02-02 23:27 RAID 5 parity layout left-symmetric vs right symmetric vs other choices Budai Laszlo
@ 2011-02-07 17:41 ` Beolach
0 siblings, 0 replies; 2+ messages in thread
From: Beolach @ 2011-02-07 17:41 UTC (permalink / raw)
To: Budai Laszlo; +Cc: linux-raid
On Wed, Feb 2, 2011 at 16:27, Budai Laszlo <laszlo.budai@gmail.com> wrote:
> Hello everybody,
>
> can someone direct me to some documentation describing the pros and cons
> for choosing a certain layout.
> Any explanation on this topic is welcome.
>
There's very little difference between the different raid5 layouts;
the default left-symmetric should be good for almost everything.
Right/left refers to how the parity blocks are distributed between
disks, and should have no real impact on performance.
Symmetric/asymmetric refers to how the data blocks adjacent to the
parity blocks are ordered, with symmetric having a slight performance
advantage for large sequential I/O. The other raid5 layouts are
special cases for reshaping & should be automatically handled by
mdadm; or are DDF-compatible layouts, intended to give "a basic level
of interoperability between different suppliers of RAID technology"
[5].
Links for more detailed info:
1 - http://www.issociate.de/board/goto/25704/raid5_parity_algorithm.html
- the next two links I got from here.
2 - http://www.accs.com/p_and_p/RAID/LinuxRAID.html
3 - http://www.pdl.cmu.edu/PDL-FTP/Declustering/ASPLOS.ps - Post Script file.
4 - http://www.mail-archive.com/misc@openbsd.org/msg90952.html - from
OpenBSD's mailing list, questioning their use of left-asymmetric as
the default, when symmetric is expected to have a slight advantage for
large sequential I/O, and the thread starter hadn't been able to find
any advantages for asymmetric. Linux MD raid defaults to
left-symmetric.
5 - http://www.snia.org/tech_activities/standards/curr_standards/ddf/
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2011-02-07 17:41 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2011-02-02 23:27 RAID 5 parity layout left-symmetric vs right symmetric vs other choices Budai Laszlo
2011-02-07 17:41 ` Beolach
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.