Two HDDs in RAID 0 act as one drive

Asked By amirn2009 10 points N/A Posted on - 07/19/2011

I was looking online today to try to come up with an answer about RAID and its abilities and drawbacks.

However, one question that I couldn't find an answer to is if you can have two HDDs in RAID 0 (striped), then have one HDD act as a mirror for the other two.

In other words, if two HDDs in RAID 0 act as one drive, then can I add another larger hard drive and set that up with the other HDDs to achieve a complete mirror.

I don't necessarily want to use the larger HDD for data access, but I do want it so that if one of my other drives fails, I always have a mirrored backup to use while I rebuild my RAID 0 configuration.

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Answered By Djohn 0 points N/A #84856

Two HDDs in RAID 0 act as one drive

Hi Amirn,

First of all let’s understand what is RAID (Redundant Array of Inexpensive Disks).The Raid is a disk organization used to improve performance of storage systems by an array of disks controlled through a controller called RAID Controller.

So data are distributed over disks (striping) to allow parallel operation. In RAID 0 there is no redundancy to tolerate disk failure. Let say each strip has K sectors and it’s organized as strip 0: sector 0 to k-1 and strip 1: k to 2k-1 …etc.

This works well with large access and less reliable than having a single large disk. I suppose you to use RAID 1(mirroring) which uses twice as many disks as does RAID 0(first half: primary, next half: backup) to duplicate all disks without using a large disk for backup.

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• Posted on - 07/27/2011
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Answered By Patrick b 0 points N/A #84857

Two HDDs in RAID 0 act as one drive

Hello Amirn2009.

Yes.  That will work.  It's called a "RAID 0+1" (actually there's a lot of confusion as to how nested RAID configurations are called).  However, be aware that such a configuration has a weakness. 

If the RAID 0 fails (that is, if one of the disks in the stripe fails) you will be running on 1 hard drive only.  If that 1 hard drive fails while rebuilding the RAID 0, then you lose all data. 

Another problem is that it might not work with hardware RAID since most hardware RAID controllers expect an even number of hard disks.  It will work on software RAID though which in itself is another weakness because software RAID tends to fail more often than hardware RAID.

Hope this helps!

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• Posted on - 10/01/2011
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