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Re: how many disks can be in a raid-5 lun in an FC60?

 
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Sean OB_1
Honored Contributor

how many disks can be in a raid-5 lun in an FC60?


I need to know if I can create a lun with 12 disks in it as raid-5 in an FC60 array.

Can this be done?
12 REPLIES 12
Sean OB_1
Honored Contributor

Re: how many disks can be in a raid-5 lun in an FC60?

Thanks Pete. I'm trying to find out if I can increase a current lun from 6 to 12 disks, or if I'll have to create a second lun let LVM stripe the data across the two luns.
Pete Randall
Outstanding Contributor

Re: how many disks can be in a raid-5 lun in an FC60?

Sean,

I believe you can. The "User's Guide" suggests adding more disk to your RAID 5 LUN "to increase both performance and storage efficiency" without specifying any maximum. There is one example with 6 disks so we can assume that at least that many are permissable.

Pete

Pete
Pete Randall
Outstanding Contributor

Re: how many disks can be in a raid-5 lun in an FC60?

Sorry I couldn't come up with anything definitive - still looking, though.

Pete

Pete
Pete Randall
Outstanding Contributor

Re: how many disks can be in a raid-5 lun in an FC60?

Sean,

Still not the ultimate answer but I found that the old Model 20 (Nike) arrays could "have 3 to 16 modules bound as a RAID-5 group."

Pete

Pete
Christopher Caldwell
Honored Contributor

Re: how many disks can be in a raid-5 lun in an FC60?

You should make to LUNs (6 each) instead of 1 LUN (12 each). You lose data resiliency if you go more than 6 deep on a LUN (you'll lose data in certain failures).

Sean OB_1
Honored Contributor

Re: how many disks can be in a raid-5 lun in an FC60?

Chris,

Can you give more information on this? In what situation would you lose information with more than 6 disks in the lun?
Christopher Caldwell
Honored Contributor

Re: how many disks can be in a raid-5 lun in an FC60?

Fully loaded FC60 is
6 rows with 10 disks each.

This arrangement will handle a single disk failure, a single BCC failure, a single channel failure, or a single controller failure.

If two adjacent disks (in the same row) are in the same LUN, then you lose two disks in a channel failure - thus you lose data integrity with RAID5.

Here's a quote from the admin guide:

"If you attempt to select disks in the same enclosure or on the same channel when binding a LUN, you will be warned that dong so may compromise high availability."
Eugeny Brychkov
Honored Contributor

Re: how many disks can be in a raid-5 lun in an FC60?

Chris made 10+ points indeed!
Pete Randall
Outstanding Contributor

Re: how many disks can be in a raid-5 lun in an FC60?

Actually, I think Sean now has a choice to make between high availability and ease of use. It depends entirely on his situation.

Pete

Pete