12H array setup for performance

[Lacrosse]

Just trying to figure out a few limitations and best setup for performance. We have a 12H with 96GB 18GB drives. It seems we can only have 20GB max partitions total 7 ??? I am told small partitions are better for performance but we are limited by the number of partitions = 7 to utilized all the disk space what would be the best comprimise of space utilization and performance

[Ted Ellis_2]

the AuotRAID feature of the array is very interesting. The issue of using as many partitions as possible is a good one, as you can then balance load from the server from multiple paths. One thing you should consider is the RAID configuration. Keeping the used space under 50% can allow the 12H to utilize a RAID 0+1 configuration, which is far superior to RAID 5... if you use up more than the 50%, than the system will revert to RAID 5 and performance will be impacted accordingly.

Ted

[Steve Labar]

I generally spread RAID across 2-3 LUNs. I would not recommend spreading across all 7 LUNs. If you need to add/expand later, you will have to reconfigure the entire RAID to accomodate. HP also recommends not including all available disk space to a LUN. Any unused area will automatically be include for RAID 1/0 for better performance.

Good Luck.

Steve

[David Bell_1]

The functionality of the Model 12H disk array is somewhat different. The amount of space used depends on many factors.

There are a MAXIMUM of 8 LUNS numbered 0-7.
If using a "hotspare", your overhead will be equivalent to that of the largest disk. If all of your disks are 18GB, your overhead will be 18GB for the hotspare alone.

AutoRAID will use RAID 0+1 until you exceed 50% utilization. At that time, an algorithm will determine what data should be placed into RAID 5. The remaining data will remain in RAID 0+1. The significance is that as you begin to utilize more space in LUNS, more data is forced into RAID 5. As this occurs, performance will suffer.

The bigger problem is how much "free" space you have that is NOT allocated to LUNS. This allows the AutoRAID to perform at it's optimal level.

Maximum performance is also obtained if you have two HBA's (Host Bus Adapters) connected to this device. By utilizing both controllers simultaneously, you can drastically improve performance.

I would suggest you take some time to read over the manuals provided here:

http://www.hp.com/cposupport/manindex/hpsurestor19162_eng_man.html

Hope this helps,

Dave

[A. Clay Stephenson]

You can LUN's that are much bigger than 20GB. The limit is smaller if you configure from the front panel but if you configure using the Array Manager software then your LUN's can be much bigger than 20GB.

There is absolutely no advantage to more than 2 LUN's per volume group. If this is a UNIX setup then each
LUN which comprises the VG should be equal in size. LUNA should be configured so that the primary path is using controller X (alternate Y) and LUNB should utilize Controller Y as primary (alternate X). You then stripe each LVOL across both LUN's in 64k chunks.

Also, as has been indicated, try to limit the total size of all allocated LUN's to about 50% capacity so that the array stays in RAID 1/0 at all times.

If you increase the number of LUN's there will APPEAR to be less disk utilization but overall throughput will not be improved. All that performance tools like Glance know it that an awful lot of I/O is going through what it thinks is 1 disk. Performance tools have no way to know that this is an array.