From: Ethan Wilson <ethan.wilson@shiftmail.org>
To: linux-raid <linux-raid@vger.kernel.org>
Subject: Re: Speeding up reading with RAID1 and --write-mostly
Date: Sat, 13 Sep 2014 13:56:54 +0200 [thread overview]
Message-ID: <54143106.6030501@shiftmail.org> (raw)
In-Reply-To: <20140913060143.GA15849@fishbowl.rw.madduck.net>
On 13/09/2014 08:01, martin f krafft wrote:
> Assuming there is a MMC fast enough out there, how about creating
> a RAID1 across MMC and parts of the rotational disk, with the
> rotational disk flagged --write-mostly? This RAID would then hold
> the system, while the data would sit on the rotational disk.
1) Firstly, MMC, SD etc are all very slow in random access. They are
optimized for physical size and not for speed.
2) Secondly, in order to use --write-mostly, you need two devices of the
same size, so you need an MMC as big as your HDD.
Something different from (2) is called SSD-caching, and in Linux kernel
there are two approaches to do that, one is dm-cache and the other is
bcache. Both are very young and I don't know how much stable.
next prev parent reply other threads:[~2014-09-13 11:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-13 6:01 Speeding up reading with RAID1 and --write-mostly martin f krafft
2014-09-13 11:56 ` Ethan Wilson [this message]
[not found] ` <CAH3kUhGEaon77fpNm2mjRwPbNMZe9BLK3eA6LTB4xQeg0hMF-Q@mail.gmail.com>
2014-09-13 16:23 ` martin f krafft
2014-09-15 4:11 ` NeilBrown
2014-09-15 7:44 ` martin f krafft
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