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

From: Mike Fedyk
Date: Thu Jun 24 2010 - 00:51:20 EST

On Wed, Jun 23, 2010 at 8:43 PM, Daniel Taylor <Daniel.Taylor@xxxxxxx> wrote:
> Just an FYI reminder. ÂThe original test (2K files) is utterly
> pathological for disk drives with 4K physical sectors, such as
> those now shipping from WD, Seagate, and others. ÂSome of the
> SSDs have larger (16K0 or smaller blocks (2K). ÂThere is also
> the issue of btrfs over RAID (which I know is not entirely
> sensible, but which will happen).
> The absolute minimum allocation size for data should be the same
> as, and aligned with, the underlying disk block size. ÂIf that
> results in underutilization, I think that's a good thing for
> performance, compared to read-modify-write cycles to update
> partial disk blocks.

Block size = 4k

Btrfs packs smaller objects into the blocks in certain cases.
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