topic Re: VA7110 and Oracle database in Disk Enclosures

VA7110 and Oracle database

Rao Uppuluri — Thu, 03 Feb 2005 12:15:04 GMT

Hello all,
1. We have RP4440-8 and VA7110 connected via Fibre. After getting the VA7110 I came to
know that, even though it has 2 controller cards, only one is used at anytime to access
the data on the VA. I am planning to put a Oracle database on the VA7110 with tables, indexes etc in seperate luns. Since I can't have seperate physical paths for my Tables, Indexes etc, are there any tips, tricks to
acheive this goal?
2. Also, Can I allocate ALL of the "unallocated capacity" to my Luns? I plan to use the VA in AutoRAID Mode.
Thank you,
Rao

Re: VA7110 and Oracle database

Peter Mattei — Thu, 03 Feb 2005 14:23:30 GMT

Well, if you want to put Oracle on it and expect good performance I would use it in RAID1 and have as many disks as possible.
Disk performance is achieved per spindle.
On disk will give you from 50 to 200 IOPs (read) thus more disk means performance.
AutoRaid is a good thing if you need capacity with moderate performance.

Read more about RAID, VA and performance in this manual (Product overview)
http://h200007.www2.hp.com/bc/docs/support/SupportManual/c00088801/c00088801.pdf

Cheers
Peter

Re: VA7110 and Oracle database

Rao Uppuluri — Thu, 03 Feb 2005 15:03:09 GMT

Peter
My VA7110 is in AutoRAID mode. If I go to RAID1+0, do I lose any unallocated capacity? Also, can you explain why it gives you more performance in RAID1+0 than in AutoRAID? (I thought AutoRAID is RAID1+0 and RAID5 combined).

Re: VA7110 and Oracle database

Nguyen Anh Tien — Fri, 04 Feb 2005 01:40:33 GMT

HI Rao
You can create 1 LUN from All unallocated capacity. But HP recommend keep 1 disk space is unallocated.
For easy to manage, indexes,tables should create on one own pv (one LUN on VA).

Re: VA7110 and Oracle database

Peter Mattei — Fri, 04 Feb 2005 02:08:26 GMT

AutoRaid is indeed mixing RAID1 and RAID5-DP also known as RAID6.
If your allocated LUNs use less capacity than 50% of the raw capacity minus sparing, all data will be placed in RAID01.
For random reads both RAID levels are equal (about 7000 IOPs max for the VA7110)
For writes RAID1 is much faster (about 3500 IOPS R1 vs about 1000IOPS R5DP)
Here is why:
RAID1 is disk mirroring thus writes to two disks simultaneously, so 2 write IOs do disk.
RAID5DP is RAID5 with two independent parity blocks. These 2 parity blocks need to be read from disk, be modified and written back to disk together with the actual write data. This is called write penalty.
Find more details in the manual mentioned above page 47!

Now back to allocation. If you now allocate more than 50% of raw capacity to LUNs the array starts migrating least recently used junks from RAID1 to RAID5DP.
The more you allocate the more is stored in RAID5DP. The ugly thing is that if you allocate more space you usually have more servers and load and because of the AutoRaid migration the arrays write performance drops.
If you install the VA in RAID1 you just make sure that you can not allocate more than about 50% of its raw capacity.
Because the VA is a virtual array it constantly keeps reorganizing and optimizing in the background. This process is much faster if you have lots of unallocated space. The more LUNs you allocate the longer it takes to optimize (think of your PC when doing disk defrag)

Cheers
Peter

Re: VA7110 and Oracle database

Rao Uppuluri — Fri, 04 Feb 2005 10:13:54 GMT

OK. If I move from AutoRAID to RAID1+0, seems like I am gaining performance, atleast on writes. If thats the case, what am I sacrificing? I read the doc. and looks like with RAID1+0, multiple disk failures can be more of a problem. Can someone please explain if there are any disadvatanges of RAID1+0 over AutoRAID?
Also, regarding my original question 1, any tips, tricks for putting Oracle data on VA7110 are greatly appreciated.
Thanks again, all.