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I have an old /home partition, that dates back to former linux systems, and it is still in ext3 format. Whereas the rest of my system, / and some other mounted point are devices formated in ext4.

I have grasped some sites on the net that describes how to convert an ext3 partition to an ext4.

In this UL.SE question Can I convert an ext3 partition into ext4 without formatting?, there are also warnings recommending backup of the data before convertion... if ever...

So I wonder if is generally a good idea to convert an existing ext3 partition to ext4. I know it's possible, I know there is a little risk that need a back up if ever. Are there enough benefits such that I should do it ?

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You should always have a backup regardless of what you're doing. –  frostschutz Apr 22 '13 at 14:22
    
@frostschutz Yeah, we all know. We also don't necessarily have the budget for massive numbers of drives, and possibly a networked computer to do the backups. –  T.C. Apr 22 '13 at 14:36
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Do you have the budget for losing all of your data? –  mattdm Apr 22 '13 at 14:37
    
Like Peace Blaster's answer suggests. I could do one copy, one format ext4, and one copy back over the new format... in "words" it looks safer... –  Stephane Rolland Apr 22 '13 at 15:09
    
We've been using ext4 for several years in RHEL & CentOS release and we've never had a single issue related to it. We've run it both on bare metal servers & as VMs, in a 100+ computer cluster node as well as customer facing web applications. –  slm Apr 22 '13 at 17:14
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3 Answers

up vote 4 down vote accepted

Both ext3 and ext4 are journaling filesystems, in addition this list several differences, the most relevant are:

  • Maximum individual file size can be from 16 GB to 16 TB
  • Overall maximum ext4 file system size is 1 EB (exabyte). 1 EB = 1024 PB (petabyte). 1 PB = 1024 TB (terabyte).
  • Directory can contain a maximum of 64,000 subdirectories (as opposed to 32,000 in ext3)
  • Several other new features are introduced in ext4: multiblock allocation, delayed allocation, journal checksum. fast fsck, etc. All you need to know is that these new features have improved the performance and reliability of the filesystem when compared to ext3.

The interesting thing for you might be the faster fsck, the others are probably of less significance in this particular situation (unless your disk gets a growth spurt and magically can contain much larger files).

If you are not going to use that partition intensively I would not recommend converting (at least not without a backup).

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EXT4 is good in the new versions of different distros.

Don't use ext4 if you are still using older versions. Older version has some issues that have been fixed in new versions. resize unmounted volumes only to be safe.

I used a "live cd" for conversion. went smoothly.

I would recommend backups just to safe but they are just there as a pre-caution.

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I'm using Ubuntu 12.04, so it is rather recent and I apt-get update and upgrade several times a week. –  Stephane Rolland Apr 22 '13 at 15:06
    
That should be good enough. I would suggest that you re-size by booting on to live CD that way the partition is not mounted while you convert. you can also to run in single user mode "init 1" and un-mount /home and then run the command. I prefer booting into live CD. I would suggest on a back up - just in-case. –  DaveDeveloper Apr 22 '13 at 15:59
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I am running ext4 with centos 6 on multiple servers. I am running ext4 on a database running on 16 core xeon processor with 32GB ram handling about 1000 queries per second with about 1TB data and running replication at the same time. The performance is is much higher than one running on ext3. No data corruption yet. I wouldn't run ext4 on centos 5 though. –  DaveDeveloper Apr 22 '13 at 16:07
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Many server admins still are sketchy on ext4, but if you're determined to upgrade I can't think of a way to do it safely without copying everything off of it and reformatting that partition.

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+1 that's what I was also thinking... since there is still one copy needed for the back up... why not two after reformating... –  Stephane Rolland Apr 22 '13 at 15:05
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