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AutoRAID Performance

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Justin Willoughby
Regular Advisor

AutoRAID Performance

AutoRAID Performance

I am trying to increase the performance of my autoraids.

I ran the following to get a recombination of what changes I should make:

(hostname)root# arraydsp -r 09041200 09041700 arraysn

Vendor ID = HP
Product ID = C3586A
Array serial number = arraysn
Performance Recommendations (12:00 09/04/2001 to 17:00 09/04/2001):
--------------------------------------------------------------------------------
Add another disk array because the write working set is too large.

The number of write I/Os being performed by the host on a daily basis
is consistently exceeding the amount of RAID1 space available to service
them. This results in decreased performance because some writes must be
serviced from RAID 5 space. Adding another disk array to increase the amount
of available RAID1 space should improve performance.
--------------------------------------------------------------------------------

Unfortunately the way my autoraids are setup they have the whole LUN using all of available disk space so there is no raid 0/1, as arraydsp ?a arraysn shows:

Raid 0/1 capacity = 0 MB *

I also notice that arraydsp ?a shows:

Write Cache = DISABLED
Read Cache = DISABLED

The arrays are at firmware version HP25.

All the disks are used and allocated to the LUN as I mentioned. To increase raid 0/1 should I try replacing some of the 4GB drives with larger drives to give me some disk space beyond what is allocated to the LUN? How much will help with performance?

I did a ?sar ?b? and it shows 100% for %rcache and 92% for %wcache. Does this indicate I should make some change to the kernel?

Thanks!

- Justin
10 REPLIES
Dan Rosen
Frequent Advisor

Re: AutoRAID Performance

There are a few other posts through here, so you should look for "Autoraid" and "LUN".

For Autoraids, you are supposed to set up multiple LUNs for optimal performance. One of the ways to get that performance is if you have dual controllers. You can set the paths to different LUNs over exclusive controllers.

But, if you have all 12 disks in the case, AND they are all 4 gig, and all used, then you should probably upgrade to 9 gig (if you can find them) or 18 gb. While you may not need the space, you can leave the space unallocated, and then take advantage of RAID 0/1.

I attached the output of my "arraydsp -a". Note that I only have 5 disks, (grrr, stupid economy), but I didn't allocate all of my space so that I can still use 0/1.
Justin Willoughby
Regular Advisor

Re: AutoRAID Performance

I did not setup the AutoRAIDs here. You are right that more then one LUN should have been setup per AutoRAID. We only have one controler used in each AutoRAID. In order to setup more the on LUN we would need to backup and then restore all the data on these AutoRAID which would require too much downtime for this sytem which needs to be up 24/7.

I will look into the 18 drives and see how much they cost.

- Justin
A. Clay Stephenson
Acclaimed Contributor
Solution

Re: AutoRAID Performance

Hi Justin:

The bad news is that you've broken just about every rule for good AutoRAID performance. The read cache and write cache DISABLED messages
is not a problem. This only indicates the status of the caching as it appears to the outside world (i.e. the host); internally caching is always enabled. Changing this value will have no real effect. From the Product ID returned by arraydsp it looks as though your are running a Model 12 rather than a 12H. If my poor memory serves, 4GB's were the largest disks that the Model 12's supported. If you've got 12H's then you can install 36GB's. At the very least, to see any real improvement you need to install 4 new drives and morew would be better.

The other thing you must do is utilize both controllers. You are really only using one now.
The ideal setup is to actually setup each volume group as a pair of equally sized LUN's.
LUNa's primary path should be through controller X (alternate Y) and LUNb's primary path should be through controller Y (alternate X). You then stripe all lvols within that volume group across both LUN's in 64K chunks.
This will fully utilize both controllers and all four internal scsi buses. The other key
to performance is to use no more than about 60% (less is better) of the space as configured LUN's - this keeps everything in RAID 0/1 and AutoRAID performance can then be quite good.

The good news is that Model 12H's and drives are now dirt cheap on the used market.

Regards, Clay
If it ain't broke, I can fix that.
Justin Willoughby
Regular Advisor

Re: AutoRAID Performance

Clay,

You are right it seems that the 12 does not support drives larger then 4.3GB. We have on 12H but that is in another system that is not a production system and that is running fine.

We are likely going to be moving the data from the AutoRAIDs to an IBM ESS (Storage Area Network) server with in a year. I was just trying to figure out a way to increase performance until then, as the disk I/O to that AutoRAID's is very very high and according to GlancePlus a problem.

- Justin
Joseph C. Denman
Honored Contributor

Re: AutoRAID Performance

Only way to increase performance would be to:

Backup
Reconfigure autoraid
Restore

Clay has posted some good threads on autoraid configuration. I suggest doing a search on autoraid. You should find everything you need.

..jcd...
If I had only read the instructions first??
Dan Rosen
Frequent Advisor

Re: AutoRAID Performance

Sorry, I missed the nuance of the "12" vs. the "12H". I must reinforce though that if your Autoraid 12 is supposed to be 24/7, I think you are playing with fire only having one controller.

I have the 12H and yes, I just found that refurbished drives are falling under $700 for 9 GB.

If you do use your 12H, remember that you should always add drives of the same size to minimize wasted space in the RAID 0/1 arrangement.
Justin Willoughby
Regular Advisor

Re: AutoRAID Performance

Dan,

It is not as bad as it sounds. We do have two controllers and two AutoRAIDs. The AutoRAIDs are a mirror of each other and each has both controllers connected to each of them, one uses one controller as the primary and the other uses the same controller as the secondary. So one AutoRAID uses X and the other uses Y, but they should be able to use the one not being used if they have to. We should be able to lose a whole controller or AutoRAID and be ok. It would be better if each AutoRAID had two controllers to itself and had at least two LUNs but they don?t.

- Justin
Bill McNAMARA_1
Honored Contributor

Re: AutoRAID Performance

I think you've just summed it up well in your last comment.

Regarding the AutoRAIDs being a mirror of each other, do you really expect simultaneous multiple failure? You may as well just do it right and get an XP48 solution. You're talking fibre channel and fibre channel disks.

You're still sending out multiple writes with mirror disk, you may consider using fc adaptors to increase performance on the HBA side.

Bill
It works for me (tm)

Re: AutoRAID Performance

The actual problem is AutoRAID or not AutoRAID.
I have been involved in an Oracle Application 11 integration project with a limited budget.

We started with 2 AutoRAID 12H and we got poor response time. We tried to escalate this issue and got replies telling : technology bound ! So we changed our AutoRAID 12H to 2 FC10 racks, for a replacement within the same cost. We got 200% to 400% performance improvement immediately !

Searching for an advice ? change technology

Regards
Justin Willoughby
Regular Advisor

Re: AutoRAID Performance

Bruno,

I had heard the same thing about the AutoRAIDs too, (long after we had already been using them). We will be moving the data to our IBM ESS so this should help, until then I guess we will just have to live with the way the system is.

Thanks too all that have replied to this thread!

- Justin