Hot Swap -- Is it possible?

[scott_417]

If I have 6 disks in the enclosure, I put Disk 1 (72 GB) and Disk 2 (72 GB) in Array #1 (for RAID1)， and Disk 3 (146 GB) to Disk 5(146 GB) (for RAID 5) in array #2. The Disk 6 (146 GB) will be the online spare one.

1) Now, suppose the Disk 1 (72 GB) crashed, can I "hot" swap/plug the Disk 6 (146 GB) to replace the Disk 1?

--The reason I ask this is that the capacity of the Disk 6 and that of Disk 1 do not match.

2) As the case described in this question, can I configure Disk 6 to be ready for the hot swap for Disk 1 to Disk2, and also for Disk 3 to Disk 5 above?

--The reason I ask this is that Disks 1 and 2 are in one array, while Disks 3 to 5 in a different array. So the hot swap will happen for different arrays. Wonder if it possible.


Thanks to help.

Scott

[Plamen Radev · Accepted solution]

Scott,

The on-line spare, as well as the hot-swap replacement capacity should exceed the maximum equivalent disk size of your arrays.
If:
- HDD1 is 72GB
- HDD2 is 36GB
- HDD3 is 146GB
- HDD4 is 72GB
- HDD5 is 72GB (queer mixture; lots of "bytes" lost :-()
then the equivalent disk size of your Array_1 (HDD1,2) would be 36GB and the equivalent disk size of Array_2 (HDD3-5) would be 72GB (note: this is NOT the usable space on RAID5 which in the case would be 2x72GB).

Thus your on-line spare / replacement drive would have to be at least 72GB to protect both Array_1 and Array_2.

[Steven Clementi]

Scott:

2. Hot Spares can be configured to cover all arrays on a single Smart Array Controller. Your disk 6 can be a hot spare for Array A and B as long as it is the size of the largest "usable" drive size in the system.

In your case, you would nee to have a 146GB drive in slot 6. If you had a 72GB drive, it could only be hot swap for Array A.


Steven

[Plamen Radev]

Steven,

In the above example Array_B utilizes disks of following sizes:
- HDD3 is 146GB
- HDD4 is 72GB
- HDD5 is 72GB
In the case the array would be initialized according to the smallest disk size, e.g. 72GB, hence the on-line spare of 72GB would be sufficient for this array.

Unfortunately, 72GB unused space would be lost in HDD3.

[Steven Clementi]

Correct...

...but Scott's original configuration was for 3 146GB drives in slots 3, 4 and 5. He would need a 146GB disk for a hot Spare.


Steven

[Plamen Radev]

Fully agreed

Plamen