From: Alireza Haghdoost <alireza@cs.umn.edu>
To: Tejas Rao <raot@bnl.gov>
Cc: NeilBrown <neilb@suse.de>, Scott Sinno <scott.sinno@nasa.gov>,
Linux RAID <linux-raid@vger.kernel.org>,
"Knister,
Aaron S. (GSFC-606.2)[COMPUTER SCIENCE CORP]"
<aaron.s.knister@nasa.gov>
Subject: Re: clustered MD - beyond RAID1
Date: Mon, 21 Dec 2015 20:29:56 -0600 [thread overview]
Message-ID: <CAB-428=ekQPx_ia1Xtx-hDTX8squ2W9ZN5YrVgf=4nbW2erMhQ@mail.gmail.com> (raw)
In-Reply-To: <5678A908.6070401@bnl.gov>
On Mon, Dec 21, 2015 at 7:36 PM, Tejas Rao <raot@bnl.gov> wrote:
>
> We currently have 10's of petabytes in production using linux md raid. We
> are currently not sharing md devices, only hardware raid block devices are
> shared. In our experience hardware raid controllers are expensive. Linux
> raid has worked well over the years and performance is very good as GPFS
> coalesces I/O in large filesystem blocksize blocks (8MB) and if aligned
> properly eliminate RMW (doing full stripe writes) and the need for NVRAM
> (unless someone is doing POSIX fsync).
>
Full Stripe Write does not eliminate the need for NVRAM. Stored data
under MD RAID-6 is vulnerable to write-hole data corruption issue.
Yes, hardware RAID controllers are expensive because they would
provide more data reliability and high-availibiltiy that might not be
useful for this use case.
--Alireza
next prev parent reply other threads:[~2015-12-22 2:29 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-18 15:29 clustered MD - beyond RAID1 Scott Sinno
2015-12-20 23:25 ` NeilBrown
2015-12-21 19:19 ` Tejas Rao
2015-12-21 20:47 ` NeilBrown
2015-12-21 21:27 ` Tejas Rao
2015-12-21 22:03 ` NeilBrown
2015-12-21 22:29 ` Adam Goryachev
2015-12-21 23:09 ` NeilBrown
2015-12-22 1:36 ` Tejas Rao
2015-12-22 2:29 ` Alireza Haghdoost [this message]
2015-12-22 4:13 ` NeilBrown
[not found] ` <CAB9NSeXhoHd3_BDRrWAsBrW0Dj2=NucyUFt8pSP0zB5K=RkUOg@mail.gmail.com>
2016-12-05 1:46 ` Aaron Knister
[not found] ` <5678A2B9.6070008@bnl.gov>
2015-12-22 1:50 ` Aaron Knister
2015-12-22 2:33 ` Tejas Rao
[not found] ` <5678B693.40907-IGkKxAqZmp0@public.gmane.org>
2015-12-25 8:47 ` roger zhou
-- strict thread matches above, loose matches on Subject: below --
2016-12-02 18:12 Robert Woodworth
2016-12-02 20:02 ` Shaohua Li
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