Any Raid Experts?

[Piru]

I am planning to build a new computer and I wanted to get some advice on Raid5 and Raid 1+0.

Personally I use a large NAS (4 x 1.5TB HDD) and a server (3 x 1.5TB) RAID-5 setups to store data. My desktop machines have only relatively small SSD HDDs. The NAS/server storage is available to all my computers in my home LAN.

If you're going to use large capacity drives, use RAID-6 rather than RAID-5. I already am pushing it with RAID-5 containing 4 1.5TB HDDs. If one of those HDDs should fail, it already is quite likely that 2nd one fails during the rebuild.

Also, as already mentioned RAID itself doesn't replace backups. So remember to backup our important data even when using RAID.

[Piru]

RAID5: You will need at least 3 disks. Net. capacity will be 2 disks then.
RAID1+0: You will need at least 4 disks. Net. capacity will also be 2 disks then. Will be faster than RAID5

Small clarification: Faster than RAID5 when writing. Reading is pretty much the same.

[Piru]

I just had my first HDD failure with the RAID-5. One of the 1.5TB Barraducas (ST31500541AS) dropped dead. I've swapped the drive and added the new HDD to the array with:

Code: [Select]

sudo mdadm /dev/md0 --add /dev/sdh1The raid is now rebuilding itself:

Code: [Select]

Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sdh1[3] sdb1[0] sdg1[2]
      2930276864 blocks level 5, 128k chunk, algorithm 2 [3/2] [U_U]
      [=>...................]  recovery =  8.0% (117313844/1465138432) finish=516.8min speed=43460K/sec
     
unused devices:
This is the critical part. If the rebuilding fails due to failure in the remaining good drives I will lose the array and all data within. If it was RAID-6 I could still lose a 2nd disk without data loss.

Obviously I've backed up all important data before the rebuild, so only some less important data would be lost if 2nd disk failure should occur.