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Disk Arrays
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Add physical hdds to existing array in MSA50

Samuel Lim
Occasional Contributor

Add physical hdds to existing array in MSA50

Hi Experts,

I have a customer purchased 7 new physical disks for their MSA50.

But the manual for ACU says the following:
"In raid 5 configurations, keep the risk of logical drive failure low by assigning no more than 14 physical drives to the array."

Can anyone tell me why the drive failure risk increase when we assign 14 drives to one array.

Thanks a lot & have a pleasant day,
Samuel Lim
Stephen Kebbell
Honored Contributor

Re: Add physical hdds to existing array in MSA50


it's the risk of a "logical drive" failure. Not a physical disk failure. Logical drive failure would occur if 2 disks in a RAID 5 failed. As you increase the number of disks, the chances of 2 of them failing increases. Although that's still quite a low probability.
But that shouldn't concern you, as 14 disks is the maximum possible in an MSA500 (there is no MSA50)