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Can a RAID Array straddle multiple caddies

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Kev Swindells
Occasional Visitor

Can a RAID Array straddle multiple caddies

Hi,

I have a ML370 G6 which currently has two hard disk caddies installed in it - once of which has four disks installed and configured as a RAID array.

I wish to increase the capacity of this and wish to install a further five drives - however the caddie only has four slots remaining.

If I install the five drives across two caddies can the server still RAID them together, and if so is there any performance impact?
3 REPLIES
TTr
Honored Contributor
Solution

Re: Can a RAID Array straddle multiple caddies

Assuming you have the built-in raid controller, P410i, it only has 8 SAS ports. So you can not connect to both disk cages.

The only way you can connect to the 2nd cage is by a second raid controller, P410, or by adding a SAS expander card. Adding disks to a controller always impacts performance but it all depends on your i/o requirements.
Adding a second P410 would give you faster i/o but the two raid controllers are independent of each other you can not create raid arrays across the cages/controllers.

With a SAS expander card all disks would attach to the same controller and you could create large arrays with many disks. I/O is impacted but if you don't have high i/o demand it will be fine.

http://h18000.www1.hp.com/products/servers/proliantstorage/arraycontrollers/sas-expander/index.html
Kev Swindells
Occasional Visitor

Re: Can a RAID Array straddle multiple caddies

Hi, Thanks for that TTR.

We do have an SAS Expander card installed in the server.
TTr
Honored Contributor

Re: Can a RAID Array straddle multiple caddies

In that case you can wire both cages to the SAS expander card and then the exp card back to the P410i.

The SAS expander card takes the 8 ports from the P410i and switches them out to the 16 ports of the two cages, so there is switching taking place like in a LAN switch.

As I said before it depends on your i/o requirements. In your case with only two arrays the switching over to the second cage is not going to impact the i/o. If you add more disks and you fill up both cages you might notice some more impact to the i/o.