I've currently put together a new system and part of that has been creating a software RAID 5 using 'mdadm' in Ubuntu Server.
I successfully got to the point where I create the array using:
sudo mdadm --create --verbose /dev/md0 --level=5 --raid-devices=4 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1
I left it to do its thing overnight then used the following command to check on it:
watch cat /proc/mdstat
To which the following was returned:
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] md0 : active raid5 sdd1(S) sdc1 sdb1 sda1(F) 5860535808 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/2] [_UU_] unused devices: <none>
It appears that one has failed (and I'm not too savvy with why another is a spare).
So, just to be sure that something else isn't amiss I wanted to try and re-engage the failed drive. Can someone explain how I can do that and what I should do with the spare (if anything).
And also how do I know when synchronisation is complete?
The tutorial I used to get this far is located here:
p.s. Here is some extra information that may help:
sudo mdadm --detail /dev/md0 /dev/md0: Version : 1.2 Creation Time : Mon Jun 18 21:14:21 2012 Raid Level : raid5 Array Size : 5860535808 (5589.04 GiB 6001.19 GB) Used Dev Size : 1953511936 (1863.01 GiB 2000.40 GB) Raid Devices : 4 Total Devices : 4 Persistence : Superblock is persistent Update Time : Mon Jun 18 21:50:26 2012 State : clean, FAILED Active Devices : 2 Working Devices : 3 Failed Devices : 1 Spare Devices : 1 Layout : left-symmetric Chunk Size : 512K Name : myraidbox:0 (local to host myraidbox) UUID : a269ee94:a161600c:fb1665e7:bd2f27b3 Events : 13 Number Major Minor RaidDevice State 0 0 0 0 removed 1 8 17 1 active sync /dev/sdb1 2 8 33 2 active sync /dev/sdc1 3 0 0 3 removed 0 8 1 - faulty spare /dev/sda1 4 8 49 - spare /dev/sdd1