Ext3 users - Apr 2011 - Resizing a file system that has been converted to ext4

Hello,

I have an ext3 file system of about 8TiB in size.  At the rate data is 
added to the file system it will fill up in a few months so I'm weighing 
my options.  One option would be to create a new ext4 file system and 
copy everything over to a new, larger ext4 file system.  Another option 
would be to modify the software that uses this file system so it can use 
multiple file systems.  Finally, I could could convert the existing file 
system to ext4 and then resize it.  Is this advisable?  Has anyone tried 
this?

Thanks,
Sean McCauliff

On 4/7/11 4:08 PM, Sean McCauliff wrote:
> Hello,
> 
> I have an ext3 file system of about 8TiB in size.  At the rate data
> is added to the file system it will fill up in a few months so I'm
> weighing my options.  One option would be to create a new ext4 file
> system and copy everything over to a new, larger ext4 file system.
> Another option would be to modify the software that uses this file
> system so it can use multiple file systems.  Finally, I could could
> convert the existing file system to ext4 and then resize it.  Is this
> advisable?  Has anyone tried this?
> 
> Thanks, Sean McCauliff
Hi Sean -

Modern ext3 should be have a 16T limit just as ext4 does, so converting to ext4
doesn't really change your max fs size.

However, a fresh ext4 filesystem should in theory be a bit more e2fsck-able at
that scale and have the best feature-set.

I always recommend migration rather than conversion when possible; you'll
get the best features and performance, and run the most tested codepaths that
way.

-Eric

I'm pretty sure that I have filesystems with mixed extent- and block-mapped
files that I've resized in the past.

That said, depending on your data's importance, and your tolerance for risk
you should probably have a backup of your data anyway. At that point, starting
with a fresh ext4 filesystem and restoring from backup is also attractive for
the performance improvements of extents, as well as other format-time only
features.

My filesystems have a high turnover rate (PVR) and are not impossible to
replace, so I have been resizing in place and letting normal turnover of files
migrate to extents. I still don't have some if the newer filesystem
features.

Cheers, Andreas

On 2011-04-07, at 5:08 PM, Sean McCauliff <Sean.D.McCauliff at nasa.gov>
wrote:
> Hello,
> 
> I have an ext3 file system of about 8TiB in size.  At the rate data is
added to the file system it will fill up in a few months so I'm weighing my
options.  One option would be to create a new ext4 file system and copy
everything over to a new, larger ext4 file system.  Another option would be to
modify the software that uses this file system so it can use multiple file
systems.  Finally, I could could convert the existing file system to ext4 and
then resize it.  Is this advisable?  Has anyone tried this?
> 
> Thanks,
> Sean McCauliff
> 
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