Is it worth to make a RAID 1 plus 1 hot spare drive?

Question

I have some important data shared amoung 5 computers that I don't want to lose in any way, so I bought a Dell PowerEdge T430 server which came with the PERC H330 RAID controller and 3 drives (2 drives + 1 hot swap). I wanted to create a RAID 1 with my 3 1TB HDDs but sadly I realized that this controller allows RAID 1 with only 2 drives plus 1 hot spare drive. I searched on the Internet but I could not find any page that tells me more about it and how it works. The only thing I understood is that it works in standby and wakes up and starts to mirror once there is a drive failure and stops when you replace the bad drive. Does this also mean that I could use it as a normal drive once the mirroring is done? I can't find any crucial advantages about using this hot spare drive.

Anyway the RAID controller also allows me to create a RAID 5 using all of them, but I don't know if this is good beacuse it allows only 1 disk to fail.

What have I to do? Shall I use the RAID 1 plus 1 hot spare? If yes, for a better solution, which drive shall I use as the hot spare one?

Solution

If you don't want to loose the data do a proper backup not a RAID.

A hot spare drive is used for an automatic rebuild once a drive fails. Assume you have a RAID 1 and one drive goes bad. You need some time to replace the bad drive. You're running the risk of loosing all you data should something happen to the remaining drive. If you have a hot spare you can immediately begin a rebuild without shutting down your server.

It's for you to decide what kind of security you need and what kind of availability is necessary. A RAID5 has the added advantage of more space being available.

It is also advisable to store your backup separately from the RAID so when lightning strikes, it doesn't get fried together with the RAID array.

Comments

[davidgo]

Sorry to tell you this, but the PERC330 RAID controller is crap - it does not even have a BBWC. Depending on your OS, you may actually be better with Software RAID (or replace it with an H710).

[davidgo]

Do not use RAID5. RAID5 offers little practical protection, and is not considered a best practice if you have more then 2TB protection (It was OK until drives started getting large). RAID1 and using the extra disk as a backup is the way to go - RAID protects against hardware failure, not deletions or theft.

[Fabby]

An edit and an upvote! Exactly what I would say! :-)

[Gaia]

But having 3 (or even 4) drives in RAID 1 is better than having 2 drives + 1 (or 2) spare(s), correct? In other words, is there an advantage in having spares when you already have more than 2 drives in RAID1?

[Seth]

You can't simplify it like that. A spare serves a different purpose. A spare takes the place of an active disk after it fails. Having multiple active disks is a different scenario and it's uncommon (as far as I know) to have a RAID 1 with more than 2 disks because it's so wasteful. If you have a 4 disk RAID 1 (which is possible) you'd still only have the total storage capacity of the smallest disk.