LVM and ext3 filesystem

[K.C. Chan]

Can you give an option for ext3 fs during mke2fs on a logical volume device? I am in doubt because lvm is already journal, why would you want logical volume device on ext3? Thanks.

[Vincent Stedema · Accepted solution]

Hi Michael,

LVM allows you to create flexible data partitions that are not confined to a single disk. For instance, it allows you to create a single partition of 16 GB which spans two disks of 8 GB each.

Ext3 is a journaling filesystem (like reiserfs, jfs, xfs etc.), which provides rapid crash recovery.

Conclusion: it makes perfect sense to create journaling filesystems on top of LVM data partitions.

Regards,

Vincent

[Santosh Nair_1]

Vincent is absolutely right. LVM has nothing to do with journaling or with filesystem for that matter. I've been running LVM with reiserfs on my box for quite some time. The filesystem (reiserfs in my case) doesn't care about LVM and LVM doesn't care about the filesystem.

-Santosh

[K.C. Chan]

Thanks for your reply. Now which is better to use in conjunction with LVM, reiserfs or ext3?

On another note, for conceptual purposes; let say I've created a logical volume having size=100Mbytes and filesystem (ext3 or reiserfs). It's been in use for a few weeks, then I need to extend it (just assume we have enough extent to extend the lv). Lv has been extended successfully to 300Mbytes, Do I need to run mke2fs (some equiv. command) to alter (increase) the file system size? Is it safe? Can this be done without the fear of lost data? If this is possible, could you give an example? Thanks for your input.

[Peter Kloetgen]

Hi Michael,

both file systems have goods and bads:

reiser file system is a very modern file system with intent logging mechanism a little overhead, it is also very fast. But you can get into trouble when using reiser for the root-file-system. It's a known problem that reiser as rootfs can cause trouble with writing errors.

ext3 is also modern and very new, it also provides intent logging and so on, but you would have big problems if you use ext3 with most commercial backup solutions, because they don't support ext3- backups so far, like Omniback and some others....

So you have to find out which of these two you select.

Allways stay on the bright side of life!

Peter