RAID set up question

[robrien77]

Hello,

I have a MSI Fuzion mobo with a built in RAID controller. I just built the system with a WD 300 GB raptor 10k and I am looking to add some redundancy to my hard drive. I would also like to increase my capacity at the same time.

If I install 2 1TB hard drives that run at 7200 rpm with the raptor will I be able to run RAID 5 ok or do the 3 HDDs in RAID 5 need to be the same speed and capacity?

Thanks,
Russ

 

[compulsivebuilder]

It won't work the way you want.

If it's true RAID 5, then the amount of space available on all the drives in the RAID array must be the same. The drives don't have to be exactly the same model or speed, in fact, many RAID systems can handle different size drives, but they will only use as much space as the smallest drive - not a big hassle if we are talking about three 1TB drives, and one is a few megabytes smaller than the others. Not so much fun if one is 300GB...

I have replaced a failed 750GB drive with a 1TB drive on a running five drive RAID 5 system, and it works fine (as a 750GB!). I was able to replace the other four 750GB drives, one by one, with RAID rebuilds in between, with 1TB drives. When I finished, I was able to expand the RAID 5 volume to use the full 1TB on each drive. That was on a Thecus n5200 Pro NAS - not all RAID 5 controllers offer expansion. (I had multiple backups of the data on the NAS, in case the rebuild failed - I guess that's why it didn't!)

When you build a RAID 5 array, the data is striped across the drives. This means that you don't get to keep your existing data - are you prepared to lose everything on your 300GB drive?

If you bought a second Raptor, you might be able to construct a RAID 1 (mirrored disk) - some systems will replicate the used drive onto a blank (just make sure it doesn't replicate the blank onto the used drive...). That would get you some data redundancy.

Otherwise, you could make a RAID volume out of 2TB drives, and keep the Raptor as a single drive.

 

[Houndsteeth]

Are you looking for improved uptime performance? Because you can accomplish a certain level of redundancy by buying another Raptor 10K and not experience any loss of performance, which you would with the RAID 5 setup (as well as wasting space on the 1 TB drives).

One of the things I have been doing recently with my latest build (which uses an SSD) is an automated backup of my SSD as part of the shutdown process. The machine is set to back up the SSD to a disk image on the 2 TB mirrored array (2x2TB 7200 RPM Seagates). This way, if the SSD takes a dive, I can boot off a backup volume (separate entirely from both sets of disks) and attempt to restore the SSD from the backup. If the SSD is completely hosed, then I can install another disk and recreate the boot volume from the backup.

I have tested it, so I know it works. Also, the 2 TB array is back up nightly to an external drive. So, if things get particularly nasty, I'm never really out more than 2 days of stuff.