Reducing the number of devices in a RAID-5

(This blog entry has already been published in French on Nibbles' microblog)

Since 2006, linux RAID allows to grow a RAID-5 volume by adding new devices, and thus allowing to grow the filesystem underneath in order to have more free space. The opposite operation was missing, that is shrinking a RAID-5 volume by removing devices, assuming the underneath filesystem has already been reduced (otherwise data would be lost).
This summer, Neil Brown developed this feature among others, as he announced on his blog.

SATA2 and linux software RAID performance

A server I have to manage has 9 SATAII disks of 1TB each. Six of them are plugged directly to an ASRock motherboard, and three of them on a Promise PCI card providing 4 SATA II ports. These disks are partitioned on the same design: 2 partitions, a small one (1GB) for a RAID-1 and a the remaining for a RAID-5. I am therefore not using dedicated hardware but the great software RAID implemented in linux kernel.