[Novalug] NAS Box using software RAID

Jeff Stoner leapfrog@freeshell.org
Mon Jul 12 09:29:53 EDT 2010


On Mon, 12 Jul 2010, Jay Hart wrote:

> I'm standing up a new NAS Box (using FreeNAS) using matching 1TB Drives (total
> of two drives).  System disk will be a USB flash disk.
>
> 1. What is the best combo to use for these two drives?

Mirroring for 1 TB of space, LVM for 2 TB of space. I suppose you could do 
RAID 10 if you half each drive but I've not tried that.

> 2. Also, should I partition the drives to use 2 500GB partitions and leave the
> last half of the drive unused.  Would this allow for easier recovery?  Maybe

Recovery from what? RAID technology only protects against physical errors, 
not file system corruption. Only backups protect against physical and 
logical (file system corruption) errors. Of course, that assumes the 
backups are valid and you run periodic restore tests to confirm.

Splitting a drive may allow you to recover some data from media errors 
affecting that one partition, but do you really want to continue using a 
drive with media errors?

Mirroring lets you limp along on a single drive until you can replace the 
failed drive.

> setup up a second RAID drive on the last half of the disk and mirror the
> first.
>
> 3. I'm thinking I need to go procure a spare identical drive for recovery in
> case one goes bad.

Well, if you use mirroring on the NAS, you can use the spare drive as a 
backup medium.

> 4. What would be the best plan to use for a 2 drive RAID system?

You only have 2 options (in my mind) - striping and mirroring. As I said, 
you might be able to do RAID 10 with some partitioning but it's not 
something I've tested.

> 5. Will 2GB of RAM be sufficient for a TB of RAID 5 storage.  I think it
> should be, as use of the drives will be low.

RAID 5 with only 2 physical drives? Where are you going to write your 
parity bits?

> 6. Does anyone know a way to backup Windows drives automatically to a NAS
> device?  I can do it manually, but I'm looking for a utility I can tell which
> directories to backup and the timeframe this needs to occur.

While not specifically a backup program, I use Dsynchronize to keep my 
laptop drive synced to a USB drive. It works nicely for this. A single 
executible, no installer, no frills - http://dimio.altervista.org/eng/


--Jeff

"You cannot unsay a cruel word." - Unknown




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