[CentOS] unofficial ext3 and ext4 compare

[Thomas Harold]

On 6/27/2011 8:10 AM, Jerry Geis wrote:
> I have something like 300G I routinely backup.
> This includes some large 12Gig images and other files.
>
> I had been using ext3 on an external USB disk for part of the process.
>
> Under ext3 doing "rsync -a /home /mnt/external_back/backup.jun.27.2011"
> it took 200 minutes.
>
> I took the same computer, same external HD and reformatted it for ext4
> (mkfs.ext4 /dev/sdd1).
> I then started the same rsync as above. The time was reduced to 170 minutes.
>

A time reduction for using ext4 in that scenario does not surprise me. 
Under ext3, deleting large mult-gigabyte files requires a lot of 
activity as it tracks down and marks the blocks as free.  In ext4, this 
process is a lot faster due to the use of extents to track which blocks 
are used by large files.

Just the faster deletion times with ext4 might account for the time 
difference.  Under ext3, deleting a 10GB file might take a minute or 
two, but it will only take a few seconds under ext4.

(It's the primary reason that I started using ext4 last year for any 
shares / file systems where I needed to store large files.)