From: Cory Coager <ccoager@gmail.com>
To: Roberto Spadim <roberto@spadim.com.br>
Cc: linux-raid@vger.kernel.org
Subject: Re: support for external persistent cache
Date: Wed, 19 Jan 2011 12:02:52 -0500 [thread overview]
Message-ID: <20110119170252.GA891@erebus.underworld.local> (raw)
In-Reply-To: <AANLkTikZmu3uNjv_PehWOx6JWcTP60nVVLR_UeS_0wJi@mail.gmail.com>
On Wed, Jan 19, 2011 at 02:44:31PM -0200, Roberto Spadim wrote:
> yes, a jornaling but using ssd first and sata after
> it?s not raid feature...
> it?s per disk filesystem feature...
> we could implement jornaling in raid too...
> but?s more inteligent (easy) at application level (filesystem)
> you could write first at network (if it?s faster than sata) and after
> at sata (if it?s slower than network)
>
> it?s not a raid feature... it?s a per device feature got it?
> maybe a device (not raid..) for a cache division on devices
> for example
>
>
> /dev/sda (sata 1terabyte 100mb/s)
> /dev/sdb (ssd 1gigabyte 1000mb/s)
>
> /dev/cache_a (a mix of sata and ssd with sata size 1terabyte, and
> mixed speed (memory, ssd, sata))
>
> cache_a device should know that
> early reads/write should be writen to sdb
> time in time it should sync at sda
>
> the same happens with memory (ram memory) but it?s volatille (diferent
> than ssd that?s not volatille)
>
> /dev/sdb should be sync
> /dev/sda should be async (since /dev/sdb make it safe to use async)
>
>
> that?s you intention? i don?t know if linux have it, anyone know?
I would use a physical ramdisk over a ssd but thats besides the point.
They are still disk drives to the OS.
Yes, I guess it would be similar to journaling but done in RAID
itself. I don't believe it exists yet, thats why I'm asking if
we could add support for this?
next prev parent reply other threads:[~2011-01-19 17:02 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-19 3:06 support for external persistent cache Cory Coager
2011-01-19 3:12 ` Roberto Spadim
2011-01-19 3:17 ` Roberto Spadim
2011-01-19 3:34 ` Cory Coager
2011-01-19 15:19 ` Roberto Spadim
2011-01-19 15:52 ` Cory Coager
2011-01-19 16:16 ` Roberto Spadim
2011-01-19 16:17 ` Roberto Spadim
2011-01-19 16:20 ` Roberto Spadim
2011-01-19 16:29 ` Cory Coager
2011-01-19 16:44 ` Roberto Spadim
2011-01-19 16:57 ` Roberto Spadim
2011-01-19 17:04 ` Roberto Spadim
2011-01-19 17:19 ` Cory Coager
2011-01-19 17:22 ` Roberto Spadim
2011-01-19 17:02 ` Cory Coager [this message]
2011-01-19 17:09 ` Roberto Spadim
2011-01-19 17:15 ` Roberto Spadim
2011-01-19 17:20 ` Roberto Spadim
2011-01-19 17:29 ` Cory Coager
2011-01-19 17:37 ` Roberto Spadim
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