The Model 12H AutoRAID is relatively new to MPE. And RAID, as a concept, is relatively new to most MPE System Managers. There have been many questions on HP3000-L about RAID in general and the Model 12H in particular. Unfortunately, there is little performance data available. Some general questions:

is it true that the 12H is supported as of MPE/iX 5.5 PP7 (plus supplemental patches)?

can it be used for the system volume set (including ldev 1)?

can ldev 1 be on a 9GB drive?

are there any performance issues?

From Bill Lancaster:

The 12H (AutoRAID) is supported as of MPE/iX 5.5 PP7. It can be used as the system volume set and a 9GB drive can be configured as ldev 1. But you will only be able to address up to 4GB, the same as with JBOD.

The performance implications of AutoRAID are another story. As with all things performance, ‘it depends’ is again the right answer. If you're planning on using these in a near-line storage capacity (archiving etc.) it should be fine. If you are using it in an OLTP environment with a mildly I/O sensitive application, you'll probably still be fine. If you are planning on using it in an OLTP environment with heavy I/O sensitivity you may have a problem.

There aren't a huge amount of these installed on MPE systems, but there are some. A few of my customers have them and at least one company is forcing a switch from AutoRAID to the XP256 just for performance reasons.

Our (Lancaster Consulting's) 'official' position is that:

for MPE always configure the 12H as RAID 1 (RAID 5 performance on MPE is awful)

thoroughly test the 12H in your environment before moving it into production, and

avoid significant reduction in spindle counts when moving to AutoRAID"

In a separate posting, one user of the 12H contributed the configuration they are using for everyone to see. They have a system volume set consisting of two logical drives, each 4GB and a user volume set consisting of three logical drives, each approximately 12GB.

Another user provided their experience: "We have a system on 6.0 Express 1 plus some patches with ONLY a single AUTORAID configured very similarly. Performance is as good as the same system when on a collection of internal and Jamaica discs on three FW-SCSI channels.

From still another user: "The AUTORAID handles the Raid 1 and 5 balance automagically, so there is no direct configuration of those attributes. About all one can do is ensure sufficient disc is available (outside of configured LUNs) so the AUTORAID can keep as much as needed in Raid 1. So far the balance on our system is very good. But it takes time for the data to migrate to the mode where it should eventually stay. Note we do not have large databases but do have 468,000 smallish files."

Where are we with the 12H? Some people are having good success, but at least one user is switching to the XP256 because the 12H does not provide sufficient performance. So, I guess we are still left with "your mileage may very".