hpucker99 wrote:
Tis is the first I have heard of this type of problem. I already have a RAID but will look into getting another. Do you remember who the manufacturer of the enclosure and drives were?
Actually, RAIDs leverage the performance of multiple drives to increase speed, reliability, or both. Yes, you can drop a RAID box, but you can also drop drives, displays, computers, etc. by the same token, a flood will likely disable one as will a fire, but exactly the same can be said of the computer attachéd to the RAID and any drives directly connected to it. Net-net, none of these are valid reasons to avoid the advantages of a RAID array.
There are two ways to implement a RAID. You can either use the built-in functionality of your OS (Windows has that functionality built-in, I can’t speak to Macs) with the drives located either externally or in your enclosure. Alternately, you can purchase a seperate RAID enclosure with a RAID controller built-in. I would agree that the RAID controller is one additional potential point of failure, but so is the disc controller card or circuitry in your computer, so no difference there, and if the controller fails, your data is not lost, just unavailable until you replace the controller card. Also RAIDs typically allow hot plugging and automatic rebuilds of failed drives.
If you use a RAID (and RAID levels like RAID 3 aren’t available), you can choose:
RAID 1 (simple mirroring). You get no increase in speed (unless you can read different files from both mirrors simultaneously), but you get n+1 redundancy. The cost is you pay for 2x the usable space
RAID 0+1 (striping and mirroring) you get both a 2x speed increase and n+1 redundancy. Same disadvantage as RAID 1 - you pay for 2x the usable capacity. This is the classic favorite of DBAs (data base administrators), but you’ll need at least 4 drives to implement this.
RAID 5 (block striped with rotating parity) there may or may not be a speed increase since the actual purpose of RAID 5 is to allow multiple clients to read different files simultaneously, but you do get redundancy with less “parity overhead”. For example, in a 4 drive group, you may only use 25% of the available capacity as parity (drive failure protection), allowing you to use 75% for available storage. If you lose a drive, you put in a spare, and the RAID rebuilds the data onto the new drive. This can take quite a while with the newer large capacity drives, and you’re vulnerable to a second drive failure during this time, which may take days. To protect against this, some RAIDs allow you to use double parity (sometimes called RAID 6), but this means you pay for an extra drive that is protection, not usable space.
Finally, double drive failures DO happen. It may be a nearby lightening hit, a power surge, a cooling failure or malware that propagates/corrupts both drives, and this is what a seperate backup or DR copy (preferably in a seperate physical location) is for.
Good luck with whatever you decide, and keep your precious data safe with multiple seperate copies.