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va7410 and autoraid

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Gert Svedvall
Occasional Advisor

va7410 and autoraid

We have a va7410 set in autoraid currently running raid 0+1.
Shortly we will transfer more data to the va and will then pass the 50% limit so my question is if anyone can explain to me to what raid-mode the va will switch to and how does it behave as data are growing.

//Gert
8 REPLIES
Uwe Zessin
Honored Contributor

Re: va7410 and autoraid

It is my understanding that the array normally runs in fixed RAID 0+1 mode. If the array is full, tough. You have to add more disks.

If you switch your array to AUTORAID, it will decide on its own when and how much data is converted to RAID-5DP (DP = double protection). The array will attempt to convert data that is not much in use and it is free to convert it back to 0+1. RAID-5DP consumes less space for redundancy as RAID 0+1, so you have won disk space. It will, however, keep a certain amount of capacity reserved for 0+1 for performance reasons.

Once you have turned on AUTORAID, there is no way back. Well, you can do if you re-initialize the array...
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Gert Svedvall
Occasional Advisor

Re: va7410 and autoraid

Thanks a lot for the quick reply.
We are today having one QAsystem and one TESTsystem running baan/oracle and are planning to move an old version of baan/oracle to the system, the old version is only used for reading, is it advisiable to run in autoraid mode or should we do it another way in your opinion?
Joshua Scott
Honored Contributor
Solution

Re: va7410 and autoraid

I'm sure most others here join me in saying that autoraid (which ends up being raid5 if you use a lot of space) is NOT advisable for a database. Write performance is crushed by the overhead of autoraid, so I would say that as long as you can, operate in raid 0+1 only.

If you have the VA7410 set in RAID 01 only, then you can go up to 100% of available capacity allocated to LUNs. It will stay in RAID 0+1 regardless.

Josh
What are the chances...
Uwe Zessin
Honored Contributor

Re: va7410 and autoraid

Gert,

I beleive running in AUTORAID (I understood you initial message that the array does already is switched) is OK. The array will keep at least 10% capacity for RAID 0+1, but reading from a RAID-5(DP) still gives you the advantage of disk striping.
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Sijesh
Advisor

Re: va7410 and autoraid

As data size increases it automatically swith the Raid level to RAID5(dp).
Still all the frequently used data will be in RAID1 for better perfomance.


Sijesh
Scott McCort
Advisor

Re: va7410 and autoraid

The AUTORAID will start out with all data at 1+0. Once it reaches over 50% full it will start using RAID5-DP. It will maintain as much data in 1+0 as possible. It analyzes the data usage and puts the low I/O intensive data in the RAID5 section. This reallocation to RAID5 is done during non-busy times. As the drive continues to get full, more data will be allocated to RAID5. Fully loaded you will have 10% RAID 1+0 and 90% RAID5.
Gert Svedvall
Occasional Advisor

Re: va7410 and autoraid

Then I think I've got the picture clear, thanks a lot.
Peter Mattei
Honored Contributor

Re: va7410 and autoraid

I suggest you first examine the current performance pattern before deciding. Use the whitepaper mentioned below.

Have a look at the User and Service Guide on http://h200002.www2.hp.com/bc/docs/support/SupportManual/lpg60187/lpg60187.pdf
Starting on page 13 you will find a product overview including performance figures for RAID01 and RAID5DP.
A detailed introduction to VA performance can be found in this whitepaper:
http://www.hp.com/products1/storage/products/disk_arrays/infolibrary/va_perf_analysis.pdf

Enjoy
Peter
I love storage