Plans for BTRFS in Fedora

Eric Sandeen sandeen at
Wed Feb 23 18:33:51 UTC 2011

On 2/23/11 12:15 PM, Casey Dahlin wrote:
> On Wed, Feb 23, 2011 at 11:54:58AM -0600, Eric Sandeen wrote:
>> On 2/23/11 11:42 AM, Jesse Keating wrote:
>>> On 2/23/11 5:00 AM, Josef Bacik wrote:
>>>> This would be a great thing in general since the default ext* image is
>>>> shrunk down to be installed which creates a bad fs layout which has
>>>> performance implications.
>>> Can you expand upon this more?  The filesystem is shrunk down when the 
>>> live image is built, but then once it is installed the fs is resized to 
>>> fill out the physical disk / partition it is being installed to.
>> Shrinking down the filesystem tends to scramble it a bit.  All the allocator
>> decisions that were made based on fs size at the time of install go out the
>> window as resize2fs fills in every hole it can find to maximally compress the
>> fs.
> Is there some sort of "sparsifying defrag" we could do after copying the image
> over? The dd-based install is so fast that we could actually afford another
> pass if we needed it IMHO.

Not really... e4defrag could maybe, in theory, but its still pretty unloved.

I wonder how it'd go to prep the install on a sparse image of some reasonable size,
and then do an efficient sparse copy of that onto the target.  That would save the
scrambling, at least, and still give us minimum space usage on the install disc.

> --CJD

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