Hello crispyleif
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Originally Posted by crispyleif
[snip]
If doing a fresh install, is there some parts of the OS that I should NOT put on the Logical Volume ? Some say "/boot", some say not the entire "/".. which leaves "/home" for my part..although that's of course under "/".
Say I partition a HDD in 4 different partitions (this is for testing),
is striping those 4 partitions together better (for performance) than just making one big partition of the whole HDD and make that part of a logical volume ?
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/boot cannot be on LVM because the bootloader is not LVM-capable and needs to load file(s?) from /boot to mount LVM volumes.
The / file system cannot be re-sized while it is mounted which means you have to boot from something else to re-size it. That pretty much negates all the advantages of having it on LVM (unless you're going to have a big / with /usr, /var /home and others on the same file system).
On balance, there's no benefit in putting swap on an LVM volume unless you are in an uptime-critical situation where you might want to move it from a failing disk without stopping the system.
Performance will be worse, not better, if an LVM volume comprises blocks from 4 different partitions on the same disk -- the heads will have to thrash around over the 4 partitions to find blocks that the file system has helpfully placed contiguously so they can be accessed faster!
If an LVM volume is on, say, 4 physical disks then there is 4 times as much chance of a disk failure impacting the volume. If that matters you need to combat it with redundancy so you can continue working with one disk failed.
One advantage of smaller file systems (be they on LVM volumes or direct partitions) is that, if the boot scripts decide a volume is due for checking, it doesn't take as long as checking a big file system. Boot times are more consistent.
An often-overlooked advantage of LVM is the snapshot facility which can be used to minimise data skew and reduce downtime during backups. For example a database can be quiesced, the snapshot set up and the database activated. The LVM snapshot facility minimises the database down time.
Beware that LVM partitions (that's partitions, not volumes!) cannot be re-sized yet by the likes of gparted; if you need to re-size you have to delete and recreate. LVM provides good tools to move the data to another partition before deletion but that's no good unless you have temporary space for the other partition!
Best
Charles
