Quote from BobbyMurcerFan:
Is anyone using a RAID array to backup data (mirror) your primary hd or to (stripe) span files across hds for faster access?
I've heard the stripe route is a little less stable--so it makes me hestant. However, mirroring seems like a good idea, esp. with a 2nd hd costing ~$100.
What's your experience, thoughts? Thanks a lot.
Couple rules of thumb - never stripe unless you're also mirroring the stripe set and never stripe unless you're using multiple physical disk controllers (not drives, actual controllers) and don't using striping just to get a larger virtual disk drive (use bound volumes instead).
Striping is for performance and you need more than one disk controller to take proper advantage of it (you're able to do parallel data transfers which is one of the underlying ideas behind striping). Usually striping is for servers rather than desktops. Although I have seen a couple video editing setups that used striped and mirrored disks.
Mirroring is a simple, cheap, and low impact way of creating a degree of fault tolerance and under certain conditions getting a little extra read performance out of the storage subsystem. You don't need an additional controller to mirror (unless you absolutely want maximum fault tolerance) and it'll protect you in the event of a disk crash. Note that mirroring will NOT save you from accidentally deleting or mangling files because those operations will be mirrored in realtime.
However, if you have room in your box - there is a way to using mirroring both for ongoing fault tolerance and for backup purposes. Install three disk drives. Set disk 1 as the primary and configure an initial mirror set of disk 1 mirroring to disk 2. At the end of the week, break the mirror set and re-establish the mirror of disk 1 to disk 3. Now disk 2 is a ready to go backup. You can either then back it off to tape, CD, or DVD if you want to, or just use it as a weekly rolling backup (depends on your needs). At the end of the next week, just break the mirror and re-establish the mirror of disk 1 to disk 2. Now disk 3 is the hot backup.
With mirroring active, if you encounter a fault or crash on your primary disk, the mirror disk will automatically take over without causing a system fault. In addition, if you're doing a lot of reading from the disk during some process, the system can use the mirror as a secondary source to read from and can overlap head seek times or if you elected to install a second controller can do parallel transfers (although the performance improvement isn't as high as a properly configured stripe set, it can be worth up to 10%).
Mirroring causes little or no nominal performance impact. No impact if you use a RAID controller because the mirroring operation is handled by the hardware. An almost unnoticable impact if you use software mirroring except following system reboot when the mirror disk must be completely regenerated, so there's a noticable CPU and disk subsystem slow down until the regen process completes. Note that you can still do normal operations without waiting for the regen process to complete because the mirror disk is high watermarked - however you won't have a fault tolerant disk environment until the mirror is completely regenerated.
