smart array 641

[Tim Bitting]

I have a Proliant ML350 G3 with a smart array 641 with 3 drives in a raid 5 and need to set it up as a raid 10. I need to know if this controller will support a raid 10, and if so can I add 3 more drives in a raid 5 array and mirror the two raid 5 (Raid 10 I believe if not tell me).
Thank you

[Tim Bitting]

ok after re-reading I see that Raid 10 is a mirrored set that's striped ie. 1+0 if thats the case and if the controller will do it, is there anyway to get there from where I am with out rebuilding the server?

[Blazhev_1]

Hi Tim,

no matter which RAID Level you want to use, you can create logical drive from physical drives only, not from a logical.

This means you can't make a new log drive (RAID 1+0) from 2 other log drives(Raid 5).

You can either make another logical drive from 3HDDs and have 2 separate RAID 5.

or extend the array to use the 6HDDs in one RAID 5 log drive

or add the 6 drives(extend the existing array) and then migrate to RAID 1+0(not recommended, because you will lost the space of the 3 HDDs...)

Regards,
Pac

[Tim Bitting]

Thanks for the reply. This change to Raid 10 is driven by a sofware requirement and I understand that I will lose the 3 mirrored drives space but I should gain 1 of the raid 5 drives back so a net gain of 1/3 more space. True? other then the lost space is there any other reasons? and will the controller do it? if I look at the user manuals they say 1+0 but the spec online say 0+1 you can find both here.
http://h18004.www1.hp.com/products/servers/proliantstorage/arraycontrollers/smartarray641/index.html?jumpid=reg_R1002_USEN

Thanks agian.

[David Kirk_2]

Tim,

With RAID 5 you would lose the space of 1 of your drives for redundancy. If you then mirror that, then you would be losing the space of 4 drives for redundancy.

So, if you were using 72GB drives, you would have 144GB of space and 288GB of space reserved for redundancy.

If I had 6 disks and I wanted good redundancy, I would suggest either RAID 5 over 5 disks with an online spare, or RAID 0+1 where you stripe over the first 3 disks and then mirror that.

RAID 5 with a spare would give you the use of 4 of your 6 disks, and if one fails, then the spare should kick in automatically.

RAID 0+1 would give you the use of 3 of your disks. If any one disk fails, then you just use the other half of the mirror until you replace the faulty disk and re-sync the mirrored set.

If you do the RAID 0+1 you will have to trash your existing array and start again from scratch. You should be able to extend your existing RAID 5 with 2 more disks and an online spare, but I've never tried it myself.


Good luck

David Kirk