From: john terragon <jterragon@gmail.com>
To: Austin S Hemmelgarn <ahferroin7@gmail.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: is it safe to change BTRFS_STRIPE_LEN?
Date: Sat, 24 May 2014 22:01:01 +0200 [thread overview]
Message-ID: <CANg_oxznQP=veRsxpcy1T_RArmz_SLM3=9_Vsw-Hn++RebVk7A@mail.gmail.com> (raw)
In-Reply-To: <5380EDF7.6010606@gmail.com>
Yes the btrfs-tools would have to be recompiled too ( BTRFS_STRIPE_LEN
is defined in a volumes.h in there too).
And yes, kernel and tools would certainly kill any raid0 btrfs fs and
maybe any other multidevice kind of setting.
On Sat, May 24, 2014 at 9:07 PM, Austin S Hemmelgarn
<ahferroin7@gmail.com> wrote:
> On 05/24/2014 12:44 PM, john terragon wrote:
>> Hi.
>>
>> I'm playing around with (software) raid0 on SSDs and since I remember
>> I read somewhere that intel recommends 128K stripe size for HDD arrays
>> but only 16K stripe size for SSD arrays, I wanted to see how a
>> small(er) stripe size would work on my system. Obviously with btrfs on
>> top of md-raid I could use the stripe size I want. But if I'm not
>> mistaken the stripe size with the native raid0 in btrfs is fixed to
>> 64K in BTRFS_STRIPE_LEN (volumes.h).
>> So I was wondering if it would be reasonably safe to just change that
>> to 16K (and duck and wait for the explosion ;) ).
>>
>> Can anyone adept to the inner workings of btrfs raid0 code confirm if
>> that would be the right way to proceed? (obviously without absolutely
>> any blame to be placed on anyone other than myself if things should go
>> badly :) )
> I personally can't render an opinion on whether changing it would make
> things break or not, but I do know that it would need to be changed both
> in the kernel and the tools, and the resultant kernel and tools would
> not be entirely compatible with filesystems produced by the regular
> tools and kernel, possibly to the point of corrupting any filesystem
> they touch.
>
> As for the 64k default strip size, that sounds correct, and is probably
> because that's the largest block that the I/O schedulers on Linux will
> dispatch as a single write to the underlying device.
>
prev parent reply other threads:[~2014-05-24 20:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-24 16:44 is it safe to change BTRFS_STRIPE_LEN? john terragon
2014-05-24 19:07 ` Austin S Hemmelgarn
2014-05-24 20:01 ` john terragon [this message]
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