Adding disks to a RAID 4si

[Brad Marks]

I am adding four additional drives to a ds2300. Since I will now have a total of 12 drives I will need to configure multiple spanned arrays. Is there any difference in creating two arrays of six drives each v.s. six arrays of two drives each. All the documentation and forum posts I read always use two disks per array in examples.
Is there any advantage to either approach?
Thanks,
Brad

[Steven Clementi]

I am not exactly sure how an "array" works on a ds2300.. but I would think that if you have more arrays, you may end up with less available/presentable storage depending upon your RAID level.


Steven

[TTr]

First of all with a single DS2300, you will be using half (or a quarter if the DS2300 has only one bus) of the i/o throughput of the 4Si controller. Second you can not compare the two options you mention without specifying raid0+1, raid1+0 or raid5. What you should select depends on how much storage you need, and how fast the i/o needs to be. Once you decide that then you determine the number of array groups and raid type.

Ideally you would want 4 SCSI buses attaching to the 4Si, the DS2300 has one or two buses only.

[Brad Marks]

TTr, Your personal quote made me smile :).
Yes, it's unfortunate that I'm stuck with a single bus DS2300.
We are currently configured at RAID5. Since there will be more than 8 drives in the array, I have to create at least two separate, spanned arrays. I plan for the arrays to be RAID5+0.
Thanks,
Brad

[TTr]

I see, the consensus is to use RAID50 but I don't see the 6disk minimum requirement. You can create RAID5 groups with 3,4 or 6 disks in them and then stripe across them using 4,3 or 2 stripes. If you have the time run some tests based on the kind of i/o you will have on the disks (large or small files/blocks). I am afraid the limiting factor here will be the single bus that is in use on the 4Si and not the disk raid arrangement.

[Brad Marks]

The six disk minimum is being met in that I currently have eight disk drives and am adding four more to give a total of twelve.

You are right in stating that our single bus is a problem, as our system is currently disk-bound. Unfortunately, there's not a lot I can do about it presently.

So, back to my original question: For RAID5+0 of twelve disk drives, is there any advantage to creating two six-drive arrays or six two-drive arrays?

Thanks!
Brad

[Brad Marks]

I guess nobody knew the answer...