Re: Btrfs: broken file system design (was Unbound(?) internal fragmentationin Btrfs)

From: Ric Wheeler
Date: Sat Jun 26 2010 - 07:56:59 EST

On 06/26/2010 01:18 AM, Michael Tokarev wrote:
25.06.2010 22:58, Ric Wheeler wrote:
On 06/24/2010 06:06 PM, Daniel Taylor wrote:
On Wed, Jun 23, 2010 at 8:43 PM, Daniel Taylor
<Daniel.Taylor@xxxxxxx> wrote:

Just an FYI reminder. The original test (2K files) is utterly
pathological for disk drives with 4K physical sectors, such as
those now shipping from WD, Seagate, and others. Some of the
SSDs have larger (16K0 or smaller blocks (2K). There is also
the issue of btrfs over RAID (which I know is not entirely
sensible, but which will happen).
Why it is not sensible to use btrfs on raid devices?
Nowadays raid is just everywhere, from 'fakeraid' on AHCI to
large external arrays on iSCSI-attached storage. Sometimes
it is nearly imposisble to _not_ use RAID, -- many servers
comes with a built-in RAID card which can't be turned off or
disabled. And hardware raid is faster (at least in theory)
at least because it puts less load on various system busses.

To many "enterprise folks" a statement "we don't need hw raid,
we have better solution" sounds like "we're just a toy, don't

Hmm? ;)

/mjt, who always used and preferred _software_ raid due to
multiple reasons, and never used btrfs so far.

Absolutely no reason that you would not use btrfs on hardware raid volumes (or software RAID for that matter).


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