Daniel P. Berrange wrote:
> LVM vs. regular partitions is the usual deal: LVM gives you more
> flexibility. You might find that you appreciate the flexibility even
> more when you run guests.
LVM & partitions give best performance characteristics.
Thanks for your insight.
If, for example, a guest has separate /root, /boot, and swap do you
recommend as best practice a separate logical volume for each or do you
give just one logical volume to the guest for it to dice up into the
various types of file systems? Is there a significant performance
difference between these two solutions?
For us newbies using virt-install or virt-manager, it prompts for at
most one partitition (which can be a logical volume) so without editing
of the config after the fact it naturally leads to the case of using
just one logical volume for the entire guest with it dicing it up into
/root, /boot, and swap or whatever.
So, for the case of just one logical volume which has been "formatted"
during the guest install, this led to the question of how do I
generically backup and restore that one logical volume.
Every piece of documentation that I find for creating an LVM snapshot
and then creating a backup requires that the snapshot volume be mounted
to perform the backup. This led me on an adventure with device mapper
and kpartx etc during which I was able to eventually get to and backup
the inner guts of my guest but it seemed like there had to be a better way.
Is there a vanilla generic backup and restore procedure for a logical
volume (a snapshot volume of the running guest logical volume) which
does not require case-by-case knowledge of what type of file system(s)
have been mapped to that logical volume? If so, is there then also a
way to do that backup in a manner which only stores the small amount of
space actually used by the guest instead of the entire space allocated
to the logical volume? In other words, something that preserves the
idea of sparseness? This is probably a generic LVM question but I could
not find my answer in the LVM docs either.
My lack of knowledge related to the above questions is why I am
currently using image files but would love to switch to individual
logical volumes for the performance benefits.