RAID Implementation with 4 hard disks

Question

I want to implement RAID in one system. I have 4 hard disks of 2TB capacity. I want to implement RAID1. My primary aim is to copy the content of one hard disk to another hard disk. here, 2 hard disks are main disks and 2 are mirrors to main hard disks. Is this possible by RAID1?

If possible please suggest the mother board?

Thanks, GSreddy.

Answer 1

I'm afraid that depends on your RAID controller. Many only allow 2 drives for RAID 1. When you have 4 drives the usual RAID configuration is RAID 10 (mirroring and striping).

Answer 2

It is possible. The motherboard is mostly irrelevant.

The way I read your questions is as follows.

          Main disk array                    Backup disk array

         (build from two drives            (build from two drives
          in a standard mirror)             in a standard mirror)

No automatic synchronisation between the main array and the backup array.
(Thus accidentaly deleting anything on the main array will not affect the backup).

Creating a standard 2 disk mirror (aka RAID 1) can be done in many ways.

• It is bog standard. All hardware RAID card support it.
• You can do it in software (e.g. use mdadm for GNU/Linux or via diskmanagement in windows 7)
• You can use Fake RAID. In this case you get the worst combination from software and hardware RAID and it is the only solution in which the motherboard matters. Avoid like the plague.

However I would like to comment on this four drive dual mirror setup.

1. RAID is not backup. If lightning strikes you still loose all you data. If there is a fire you still loose all your data. Etc. Etc. Backups are a good thing, but a backup in the same PC is not a safe solution.
2. Why use a RAID array at all for the backup disk? Why not use a mirror (Both for the higher speed and to recover recent changes from a 1 disk failure), a single local backup disk and a remote backup (preferably keeping the latter elsewhere).
3. If you want speed: You can gain more performance by using RAID1E.

Graphically represented the most likely RAID options for 4 drives would look like this:
(RAID10 added for completeness sake)