arraydsp -r says I need "another disk"

[Brad Marks]

I'm running HP-UX 10.20 on a K-420. As the 'subject' of this post indicates, I may need more disk. I have an H/P disk array with four 18.2 disks. I have three vg's: 1 dedicated to system stuff; 1 for programs; and 1 for data. 'bdf' says that I have 12gb free on the vg dedicated to data, I'm still told I need "another disk".
Do I need another disk or do I need to create more than one vg for my data.
Glance is also giving yellow and red disk warning messages.
Any help would be greatly appreciated.
Thanx!

[Juan González]

Hi Brad,
I suppose that you have a HP AutoRAID 12H, I suppose to that you have all the space available associated to LUNS. If this is true the AutoRAID will have all data in RAID 5 which is less efficient that RAID 0/1. To obtain more data in RAID 0/1 you need free space in the AutoRAID, i.e., space not associated with a LUN.
I hope this helps but I think I can give you a better answer if you include the output of the arraydsp -a command.

Best Regards
Juan Gonzalez

[Bill McNAMARA_1]

The Logical Drive on the autoraid is spread across all physical drives in the autoraid.

The autoraid disk are N+1 for all of your data on them. ie if you loose 2 disk at the same time you lose all of your data on the autoraid.
Lets say a bit of every bit of your LUN data is on every single disk on the autoraid.

The idea of the autoraid is to make your life easy, do all raid/ disk selection automatically, but there are a few things you'll still need to be carefull with..
If you want Active spare on, you effectively will require extra physical disk space. You should make sure that on an arraydsp -a that no disks are in a state of not included or that the array is not in a state of warning (or anything other than ready) from arraydsp

4 disks is the minimum supported configuration.

Later,
Bill

[Bill McNAMARA_1]

Reading in a bit more.. arraydsp -r is to get reports/recommendations from the array, thus it's only a recommendation.. based on the fact that the autoraid is storing most of your data in Raid 5 wich is poorer performing than Raid 1/0, thus the autoraid is suggesting you add another disk so it can push your data into RAID 1/0 to make it perform better.

You want to watch out inserting a disk because the autoraid perf will take a heavy hit will the data migration takes place. You may want to insert and include the disk when your users are using the autoraid less.

Later,
Bill

[Brad Marks]

Juan & Bill,
Pleas find attached, the results from arraydsp -a. Yes, Juan, it is an AutoRAID 12H. I thought all of my data was at raid 1/0: Is it?
Thanks for your help.

[Patrick Wallek]

The AutoRaid 12H will "automagically" move data between Raid 5 and Raid 0/1 depending on how heavily the data is used, to try to optimize performace since Raid 0/1 performs better than Raid 5. This is one of those magic features of the 12H that we don't have control over.

[Brad Marks]

So, the question still stands. Do I really need more disk? Will it lessen the yellow and red warnings from glance?

[Brad Marks]

Further, a arraydsp -m for a 24 hour period during a weekday, shows SCSI Q metric to be OutOfSpec for each and every of the 24 hourly report periods! Is it disk or maybe a SCSI bottleneck?