How long should resize2fs take?

[Ted Ts'o]

On Fri, Jun 24, 2011 at 10:48:51AM +0100, Alan Pope wrote:
> Hullo!
> 
> First mail, sorry if this is the wrong place for this kind of
> question. I realise this is a "piece of string" type question.
> 
> tl;dr version: I have a resizefs shrinking an ext4 filesystem from
> ~4TB to ~3TB and it's been running for ~2 days. Is this normal?

Shrinking a file system can take a long time; it depends on how many
files are using space in the part of the file system that needs to be
evacuated for the shrink to take place.

> It's ~2TB full of data which is mostly rsnapshots of lots of remote
> hosts, so lots of little files.

Yes, that will take longer.  Resize2fs is engineered for safety, which
means it copies a lot of blocks, and then it updates the inodes, and
then copies more blocks, and then updates the inode involved, etc.  So
it's a fairly seeky operation that can take a while.

Most of the time people are growing their file systems, not shrinking
them, so we haven't done a huge amount of optimization for speed in
the shrink case.

Regards,

					- Ted