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RAID 0 question

ClaretMatt
Grafter
Posts: 79
Registered: 28-08-2009

RAID 0 question

Hi all,
Right now I have 2x500gb drives in RAID 0.  My question is this, if in six months time I decided I want to add two more 500gb drive to the array, could this be done without having to destroy and re-create the array?  I mean, if I added the extra drives, would the RAID controller allow me to tag them on to the array?
7 REPLIES
Community Veteran
Posts: 3,789
Registered: 08-06-2007

Re: RAID 0 question

Depends on the raid controller...
However, you are likely to be able to add new drives as a separate raid 'volume', then stripe the volumes together under Windows disk management (as long as they are set as dynamic disks)
eg:
Volume 1 = 2 x 500GB drives (current) - appears as 1 'drive' under Windows
Volume 2 = 2 x 1TB Drives (new) - appears as 1 'drive' under Windows
Windows Disk Management = 1 Dynamic 'drive' comprising Volume 1 and Volume 2 (2 logical disks, but 4 physical disks)
HTH
B.
(p.s.  worth remembering that the '0' in RAID 0 refers to the number of recoverable files if a drive should die Wink)
Community Veteran
Posts: 4,846
Thanks: 121
Fixes: 24
Registered: 14-07-2009

Re: RAID 0 question

Quote from: Barry
(p.s.  worth remembering that the '0' in RAID 0 refers to the number of recoverable files if a drive should die Wink)

Yes, RAID 0 gives you (in principle) twice the effective drive speed in exchange for a huge (thousandfold?) increase in the risk of losing the files on the drive!
VileReynard
Seasoned Pro
Posts: 10,825
Thanks: 250
Fixes: 10
Registered: 01-09-2007

Re: RAID 0 question

The probability of a permanent failure on a disk is independently distributed...
So the probability of a failure on N disks is approximately N x probability of a single disk failure.
If you had 4 disks you could use RAID 5 and be secure against a failure of any one disk.

Community Veteran
Posts: 4,846
Thanks: 121
Fixes: 24
Registered: 14-07-2009

Re: RAID 0 question

When a hard disk goes starts to go wrong, I reckon only about one time in 30 are you unable to use some means to recover the data on it.  But in a RAID 0 system the standard data recovery techniques cannot be applied.  A RAID 0 system has two disks so I thought perhaps the chance of either one failing causing an irrecoverable loss of data is about 30*30 = 900 times the probability of that happening with a single non-RAID disk drive. 
Community Veteran
Posts: 14,469
Registered: 30-07-2007

Re: RAID 0 question

I never recommend using raid 0 as there is the potential to loose all your data (on both disks) should you have a single drive failure. This is especially true if you are using striping where the data is stored on alternate racks on alternate disks and not sequentially from the start.
The minimum I would recommend is raid 1 where a single drive failure does mean you keep ALL your data - the only drawback is you only get half the usable space. Raid 5 is an option but I have had so many problems with drive failures and trying to recover RAID 5 systems that i try not to use it if at all possible, but instead put 2 larger drives in a raid 1 config or double up with 4 disks each arranged as raid 2 x raid 1.
As for your Q.... many of the 'motherboard BIOS' raid controllers have limited functionality meaning once you have a configuration set-up, changing it is almost impossible. So if you are using a mobo based raid solution then I doubt you can just add additional drives in the raid 0 config. If you use a hardware raid controller then it oftn comes with software to manage the raid configuration so may be possible, but again not recommended in a raid 0 config.
Finally, you should never consider a raid solution as a secure/reliable method of protecting your data in the event of a drive failure. Always have some other form of backup to tape or another disk. This is especially true for business critical data. I always ask customers.... what would happen if you PC was stolen? They may think using raid solves the backup problem but never often don't consier what happens if the whole system was lost!
.
VileReynard
Seasoned Pro
Posts: 10,825
Thanks: 250
Fixes: 10
Registered: 01-09-2007

Re: RAID 0 question

I was thinking that if, for example the chance of one disk failing on a particular day was 0.001 [Disks only last 3 years Grin
then the chances of either of them failing on a particular day would be about 0.002.
So if either fails, as you @ReedRichard says, you lose everything.

Community Veteran
Posts: 14,469
Registered: 30-07-2007

Re: RAID 0 question

Also remember it is not just bad disks that can cause raid failures... the raid controller itself can fail, as can the driver or in one case I had the main memory failed causing the system to reboot several times which eventually caused the raid array to fail - this was a raid 1 so was recoverable... a  raid 0 set-up would not be.