Oracle on an HP AutoRAID Model 12H on HP-UX 11i

[Betty Fessler]

If I have an Oracle databae on the autoraid all in one
45GB LUN with 50GB unallocated space left for
raid 0/1 processing will it ever service writes from
raid 5?

[Christopher McCray_1]

Hello,

My understanding of the "auto"raid is that it is based on the amount of space allocated. Right now you have less than 50% of your allocatable space allocated to LUNs. If you were to add another LUN, then the autoraid will make the switch automatically from 0/1 to 5.

Hope this helps

Chris

[Betty Fessler]

We are trying to prevent going
to raid5. Do you also know
whether I need to reformat the array or just delete and recreate Luns to set the array
back to raid 0/1 processing?

[Christopher McCray_1]

Hello,

On pg 1-17 of the Autoraid book under Data Redundancy, it states that this is managed by the autoraid and cannot be controlled manually. If you need to increase available space, your only recourse is to add drives, which will not be easy since HP stopped selling them some time ago. If you have an active "hot spare" you can deactivate it (not recommended). If you are just trying to increase performance, then you will have to unbind the LUN, recreate new, smaller LUNs and restore from tape.

Sorry,

Chris

[Betty Fessler]

We are just trying to setup a new db on a used autoraid so I don't need to restore anything. I just want the autoraid to think its starting
out new and prevent going into
RAID 5 if possible.

[Christopher McCray_1]

Yes, the threshold for the switch between 0/1 and 5 is based purely on what you have allocated vs. unallocated. This is a good array for most functions, but can be hindering in this area.

Good luck

Chris

[Eugeny Brychkov]

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0xdbbb7680e012d71190050090279cd0f9,00.html
Eugeny

[Christopher McCray_1]

Hello again,

Stop, hold the phone...

I've been doing some reading further and from what I've seen, if you do not exceed the LUN you are presently using, that there is (in my words) a snowball's chance in heck that you will ever service writes from raid 5. Basically, the 12h needs at least 10% of its allocatable space unallocated to service raid 0/1 writes, the theory being that 90% of the data generally remains unchanged. Only if it exceeds this will it switch to raid 5. Your entire db is within a 45 GB LUN with 50GB unallocated. See what I'm getting at?

Hope THIS helps and sorry for being a tad misleading.

Merry Christmas

Chris

[A. Clay Stephenson]

The way you phrased your question makes it difficult to answer. If the total allocated space as LUN's is less than the total unallocated space then your 12H will remain in Raid 1/0 at all times.I run Oracle on 12H's and get very good performance. Leaving 50% unllocated is half the battle; the other half is splitting the I/O over both external controllers.

You should really configure your 45GB LUN as 2 22.5GB LUN's. LUN0 should have primary path through controller X (alternate Y) and LUN1 should have primary path through controller Y (alternate x). Use both LUN's in your volume group and stripe each LVOL across both LUN's in 64k stripes. Under 11.11, I would use buffer cache for everything and don't use mincahce=direct,convosync=direct vxfs mount options.

[Jim Butler]

just delete the lun and re add it for raid one.

Let the software do all the work