From: Theodore Ts'o <tytso@mit.edu>
To: Phillip Susi <psusi@ubuntu.com>
Cc: linux-ext4@vger.kernel.org
Subject: Re: Max blocks per group?
Date: Thu, 28 Jun 2012 15:23:03 -0400 [thread overview]
Message-ID: <20120628192303.GA9054@thunk.org> (raw)
In-Reply-To: <4FEC754F.5000907@ubuntu.com>
On Thu, Jun 28, 2012 at 11:16:31AM -0400, Phillip Susi wrote:
>
> I notice that mke2fs refuses to allow more than 8 * block size blocks
> per group. Why is this? Is it not permissible to have more than one
> block for the block allocation bitmap?
No, it's not permissible; it's been a fundamental design constraint in
ext2/3/4 since the very beginning. You can, however, get the moral
equivalent by using flex_bg which moves the metadata blocks to the
beginning of an aggregated of (for example) 16 block groups of a
flex_bg. The block allocation bitmaps are allocated contiguously, so
between that and locating all of the metadata blocks of the bg's at
the beginning of a flex_bg, that should get most of what you'd want
with a larger number of blocks in a block group.
And BTW, this is already the default in ext4 (using 16 block groups in
each flex_bg).
- Ted
prev parent reply other threads:[~2012-06-28 19:23 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-28 15:16 Max blocks per group? Phillip Susi
2012-06-28 19:23 ` Theodore Ts'o [this message]
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