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HP-UX Autoraid.

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Jim Druce
Occasional Contributor

HP-UX Autoraid.


I've never posted onto this forum but I hope that someone can help me with this query.

We've got a HP K360 server with 12 disks in an AutoRAID controller. I've attached an arraydisp -i .... for more info. It's running Oracle 7 and HP-UX 10.20.

We're hitting quite major performance problems which I believe are predominantly caused by disk bottlenecks.. The autoraid is configured as RAID-5 which I believe is bad news slow etc. etc. The operating system is also installed on the autoraid LUN's.

I want to move to a conventional RAID 1+0 approach which will mean i'll need additional storage, so i'm thinking of installing 2 new internal disks for the OS and completely reconfiguring the AutoRAID from RAID 5 to RAID 1+0.. Can anyway advise on the best approach to achieve this or wether this approach is advisable?

Look forward to your response.

"I don't suffer from insanity; I enjoy every minute of it!"
Trusted Contributor

Re: HP-UX Autoraid.

Hi Jim:

If you have enough space, raid 0+1 is the best the fastest way from my point of view, however, raid 5 is not a bad choice. Speaking of performance problem, generally, it is not only because of raid configuration, if you decided to do this change, definitely you can do so, but you need plan your backup/restore in advance carefully. Good luck.

Uwe Herrmann
Occasional Advisor

Re: HP-UX Autoraid.

Hello Jim,

if there is space on the AutoRaid 12h, it works automat. with Raid1/0. If your data grow up, the Array will automatic change from Raid 1/0 to Raid5 (High water mark).
It is a good idea to take the OS on internal disks (please mirror).

See http://h20000.www2.hp.com/bizsupport/TechSupport/Home.jsp?locale=en_US&prodTypeId=12169&prodSeriesId=33733&prodSeriesName=hp+surestore+disk+array+12h




Uwe Herrmann
Steve Lewis
Honored Contributor

Re: HP-UX Autoraid.

You have 19Mb in RAID 0/1 which is a good start. Please note that space allocated to LUNS is not used as RAID 0/1 even if it isn't yet used by LVM.
Last year I upgraded an AutoRAID with 36Gb 10k rpm drives. The customers data capture exercise immediately took half the time it used to, because the drives are so much quicker and the machine had a lot more RAID 0/1 space.
Secondly I advise you to use both controllers in the AutoRAID all of the time, not to allocate different controllers for different purposes since they get individually fully saturated at different times. So if you only have one controller plugged into your host machine then plug the other one in as well.

Jim Druce
Occasional Contributor

Re: HP-UX Autoraid.

Thanks for the responses so far..

Ok, if I understand things correctly... The autoraid will adjust it's RAID level depending on the amount of disk allocated to LUNS? Based on performance / capacity..

Excuse my ignorance, i'm not that clear on how these autoraids work..

If you have 120GB of available disk space in both controllers / disk and you allocated 60GB to available online storage, will the autoraid automatically adjust to a RAID 1+0 model?

And how does the autoraid allow for different size disks.. In our example with 10 9's and 2 18's..

To be honest the approach I want to take is as follows:

Allocate a mirrored / stripe across 4 x 9gb disks and allocate this to a logical volume provide 36GB mirrored storage for our Oracle database.

Then use the other 18gb / 9gb disks as seperate lv's and mirror and use this for general storage like redo logs or as a archive area.

It's basically quite a simple approach but i've found it very effective in resolving disk bottleneck issues..

Thanks for your help on this.

"I don't suffer from insanity; I enjoy every minute of it!"
Vincent Farrugia
Honored Contributor

Re: HP-UX Autoraid.


The AutoRAID works as follows.

First of all, You CANNOT create a LUN on specific disks. All the disks are used when creating a LUN, spread equally between all the disks.

You CANNOT specify whether you want it in Raid 0/1 or Raid 5. AutoRAID automatically stores data in Raid 0/1 or Raid 5 based on how often you access the data. If data is accessed frequently, this is stored in Raid 0/1, since it's much faster, but less economic than Raid 5. If data is used less frequently, it is stored on Raid 5, since performance here is not important, so might as well store it more efficiently. This auto-migration of data between Raid 0/1 and Raid 5 is done all the time thanks to the controllers (hence the name AutoRAId, by the way).

In order to speed up your AutoRAID, you need to put as much data on Raid 0/1 as possible. This is usually done by leaving 40-50% of the AutoRAID unallocated, i.e. with no LUNs. This ensures that there is enough space for Raid 0/1 to be performed, since Raid 0/1 is essentially mirroring.

AutoRAID stores data in 90% Raid 0/1, 10% Raid 5 usually. When the LUN becomes almost full, you will notice a very big degradation of performance, since your AutoRAID will be migrating data between Raid 0/1 and Raid 5 back anf forth all the time.

When this happens, the best solution is to increase space in your AutoRAID by upgrading the harddisks. Increasing harddisks is the best solution usually, but in your case, since you already have 12, this is not possible. However, you can upgrade the harddisks to 36Gb ones. This can be done online since disks are hotplug. Remove disks ONE AT A TIME, allow rebuild, insert disk, allow rebuild, etc. until all disks are replaced. If you decide to replace disks with 36Gb ones, have 2 or more replaced, not 1, since with 1, you won't use the full space of 36Gb on the disk.

Also, if I remember correctly, 36Gb disks required a level of firmware above HP56. See document below:


Tape Drives RULE!!!
Steve Lewis
Honored Contributor

Re: HP-UX Autoraid.

Yes as Vincent said you can swap the disks one at a time, allow the rebuild to complete before plugging in the next one. Performance will be affected during the rebuild.

If you want to replace all disks in one go then you must back-up all the data beforehand, then restore it all afterwards.

The first 2 disks added will not yield any increase in performance or increase in storage, but the 3rd one will suddenly improve things, since it needs the 3rd as the hot spare for the first 2.

Allocating half the storage into LUNS will mean that nearly all is kept in RAID 0/1. As indicated, you cannot choose the disks but it still helps to have about 4 LUNS used. Do not allocate all 8 LUNS because you won't be able to expand without a major re-organisation of the array.

You need to spend some time calculating how much data is accessed most of the time, in order to give you a good idea of how much you can afford to be held in RAID 5.

A. Clay Stephenson
Acclaimed Contributor

Re: HP-UX Autoraid.

There are 3 keys for good performance from an AutoRAID and if done, you will get quite good performance.

1) Limit allocated LUN's to no more than about 60% capacity - 50% is better. This will keep you in RAID 1/0 at all times.
2) Have at least 8 drives; 12 is better still.
3) Most important: Each VG should be comprised of 2 identically sized LUN's. LUN0's primary path should be through controller X (alternate Y) and LUN1's primary PATH should be through controller Y (alternate X). This will fully utilize both external SCSI paths and all 4 internal SCSI paths. There is no benefit to more than 2 LUN's per VG. Each LVOL within this VG should be striped across both LUN's probably in 64k chunks.

When you have set this guy up correctly, you will see both controllers blinking their little
hearts out.

As has been indicated, you have absolutely no control over the physical layout of the data.

If it ain't broke, I can fix that.