VA7410 How do you RAID yours?

[SM_3]

Do you use Autoraid or RAID 1+0?

How do you decide what RAID level to use with regards to VA7410?
Raid 5
Raid 1+0
or
Autoraid?

Thanks

[Lee Solomonson_1]

There are several factors that come into play with this answer. First of all, you can convert from 1+0 to AutoRAID, but not from AutoRAID to 1+0. So from a performance perspective, 1+0 is probably a good place to start.

You also need to look at your data type. Large sequential files will read and write faster on RAID 5. Most everything else is better on RAID 1+0.

Space requirements often dictate your raid type. 1+0 yields 50% usable space, while RAID 5DP offers more usable space.

AutoRAID bounces data back and forth between RAID 5DP and RAID 1+0. The more active data is kept on 1+0, and the less active data is migrated to RAID 5DP. It also detects large sequential files, and keeps them on RAID 5DP for performance sake. So you could say that AutoRAID gives you the best of both RAID types.

To answer you question; there is no right general answer - but I hope this info helps.

[Joshua Scott]

Hi,

Some general things about the RAID levels on the VA7000 series:

Obviously, RAID 1+0 is going to be the best performance, but you will only be able to use a little less than half of the raw disk capacity.

With AutoRaid, the array will move older unchanged data to the RAID 5 level as the allocated disk space takes up more than half the array.

One advantage of the RAID 5DP level that the VA uses is that the array will be able to survive the simultaneous failure of 2 drives. This was a concern with older RAID 5 implementations. See this page for more info, it has a lot of good whitepapers on RAID performance as applicable to the VA series.

http://www.hp.com/products1/storage/products/disk_arrays/midrange/va7410/infolibrary/index.html

As for as my recommendation: If you are going to be doing a lot of small random writes, then I recommend RAID 1+0, If you do a lot of large sequential writes however, then RAID 5 may actually give better performance.

Hope this Helps!

-Josh

[Alzhy]

First.. determine your application's needs ie.. transactions per minute expected per application design. Then, do your benchmarks ... have the VA7410 present both RAID5 and RADI0+1 LUNs and compare.... If you cannot do actual application benhmarks, then run dd's on both raw and cooked filesystems on vols/lvols that are on RAID5 or RAID-+1 luns. If the difference in performance between RAID0+1 and RAID5 are not really that greate (ie. 20-30%) -- then go for RAID5 so you waste less on your raw capacity...RAID0+1 while giving you the best performance -- will give you only half of your array's raw capacity...

[Steve Bonds · Accepted solution]

We started out using Autoraid on our VA but are about to switch to RAID 1+0 because of data corruption problems when using RAID 5. The root of the problem is that the VA does not adequately communicate back to the host when it's having performance problem so the host can throttle back on writes. So instead of showing a busy disk, everything looks fine up to the point where the VA stops responding. This gives POWERFAILED messages in syslog and triggers an LVM failover to the alternate path. Unfortunately, since the VA is spammed, the alternate path isn't available either. Ultimately, LVM gets confused and drops/corrupts a small portion of the data.



We've worked this problem thoroughly with the response center and the ultimate solution was to avoid autoraid. We only started seeing this problem after the capacity upgrade, before which the VA worked flawlessly.




Next time we put in a VA, it's going in as RAID 1+0, to save us the trouble of deleting and re-creating all the LUNs to get them off RAID 5.

[SM_3]

Steve

You mention capacity upgrade, what do you mean by this?

Did you add extra disk enclosures?
How many?

Thanks

[Claudiu Schmidt]

Hi,

we have 2 VA's installed in our environment, one configured in autoraid and one in raid 0/1. When we measured performance of one application , we see on the raid 0/1, 5 times the performance of autoraid. On the other side, if you have on the raid 0/1 VA less then 2 diskspace left, and a disk will fail, VA will try to move data from raid 0/1 to raid 5.This is so heavy, that almost no IO will come through. If you insert the new disk, well , raid 5 goes back to raid 0/1, so again performance loss.
If you need performance, configure raid 0/1, but look at the free space left.

Rgds,

Claudiu