Someday I might post a quick how-to here. I already posted a maintenance document in out internal website so i am a little tired right now.
Anyhow what I ended up doing was an LVM-over-VDO-over-LVM setup like this:
-------------------------------------------------- LVM disks -- actual exposed disks -- /data1 /data2, etc ------------------------------------------------------- VGS (actual usable volume group, vg1 for example) ------------------------------------------------------- vdo1 (dedup/compression/zero-elimination) ------------------------------------------------------- Logical Volume /dev/vg0base/disk1 ------------------------------------------------------- VGS (vg0base for example) ------------------------------------------------------- PHYSICAL DISKS -------------------------------------------------------What I like about this (except for the added complexity) is that the scheme doesnt really change existing setups too much. Provisioning is done in a normal way starting from the vg1 volume group above. After set up I can pretty much forget about the lower levels and do the usual disk creation such as "lvcreate -n disk1 -L 1G vg1".
The advantages of this setup are as follows:
1. Physical disks can be added if needed. Unfortunately I had to write a maintenance manual (where I work) becuase all the elements of the stack need to be expanded as well.
2. The VDO layer is easy to expand. I wanted to over provision I can simply expand the logical size of vdo1. The upper layers will follow the size (though not automatically--maintenance manual again).
Since there was existing data already (of about 25T) I had to bootstrap from a small existing space and slowly expand the vdo layer. Fortunately the backup data were contained in separate partitions (/volumes/data{1,2,3,4}) so I was able to incrementaly migrat them, though the whole process took me a week to accomplish.
jondz
