Talk:LVM on RAID
how about continuing this entry to show how to add more drives and extend the LVM/filesystem?
Read performance on LVM is bad
I have a four 250GB disk software raid5 setup using mdadm. After extensive performancetesting I selected XFS. Following your suggestion to add LVM I did some extra performancetesting. With LVM my readperformance drops from 109Mb/s to 93Mb/s, write and re-write performance stays constant. FYI. --renzo-AT-xs4all-DOT-nl 2006/02/21
Expanding RAID5 arrays is possible
It's probably worth noting in this article that it is possible to increase the size of a RAID5 array by adding an extra drive. EVMS has been able to do this for a while (but requires the array to be taken offline). Support is now being added to the actual kernel driver and mdadm to be able to do online resizes of RAID5 arrays.
The advantage of this over just using LVM to add separate arrays is that you don't waste an extra drive for parity.
You can resize the lvm physical volume after growing a raid array!
The article states that a physical volume in an lvm can't be extended. I believe this to be incorrect. See http://www.penguin-soft.com/penguin/man/8/pvresize.html
This should simplify adding disks to an lvm on raid - just grow the raid array, resize the physical volume, extend the logical volume, grow the file system and you're done :-)
I don't yet have an lvm on raid setup. Has anyone here confirmed that pvresize works as advertised?