linux-kernel - Re: [PATCH 2/2] Btrfs-progs: Add hot data support in mkfs

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Message-ID: <AANLkTikA_S5+vv=EM8hiakG0mYfanuOpRsicpr3_TZgQ@mail.gmail.com>
Date:	Fri, 13 Aug 2010 09:12:41 -0500
From:	Ben Chociej <bchociej@...il.com>
To:	linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	bchociej@...il.com, chris.mason@...cle.com,
	linux-fsdevel@...r.kernel.org, cmm@...ibm.com, bcchocie@...ibm.com,
	mrlupfer@...ibm.com, crscott@...ibm.com, mlupfer@...il.com,
	conscott@...edu
Subject: Re: [PATCH 2/2] Btrfs-progs: Add hot data support in mkfs

On Fri, Aug 13, 2010 at 9:08 AM, Tomasz Torcz <tomek@...ebreaker.pl> wrote:
> On Fri, Aug 13, 2010 at 05:14:22PM +0400, Andrey Panin wrote:
>> On 224, 08 12, 2010 at 05:29:37PM -0500, bchociej@...il.com wrote:
>> > From: Ben Chociej <bchociej@...il.com>
>> >
>> > Modified mkfs.btrfs to add hot data relocation option (-h) which
>> > preallocates BTRFS_BLOCK_GROUP_DATA_SSD and
>> > BTRFS_BLOCK_GROUP_METADATA_SSD at mkfs time for future use by hot data
>> > relocation code.  Also added a userspace function to detect whether a
>> > block device is an SSD by reading the sysfs block queue rotational flag.
>>
>> IMHO this policy is too inflexible. What if I have large array of slow SATA
>> disks and some fast SAS ones ?
>
>  I'm hoping that this is just first cut, and future versions will have options.
> For now, it is totally unusable without a way of using mirrored SSD for
> hot data.
>  Ideally, hot storage devices should be online selectable and changeable.
>
> --
> Tomasz Torcz                                                       72->|   80->|
> xmpp: zdzichubg@...ome.pl                                          72->|   80->|
>
>

This is very much just a first cut. Our goal here was to get a lot of
the legwork and experimental coding out of the way to enable to Btrfs
to *fully* tackle heterogeneous storage in the future.

BC
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