reuse 12H disk array

[jane zhang]

Hello,

I have a N class server with 12H array hosting oracle databases. There are 8 LUNs for storing database data files. vg00 was created from a seagate drive and not part of the array.

I am having the task to reuse this server as a major file server. All the data can be erased. I have already backed up the whole system via ominiback. How do I deconfigure and reformat the disk array completely clean for the new purpose?

umount file system, deactivate volume group and vgexport, then delete the LUNs and then recreate LUNs and then vg and then lvols?

If anyone can give a detailed procedure, that would be very helpful for me who never refomated 12H disk array before.

Thanks.
Jane

[Mic V.]

Jane,

If I understand your config right, then yes, that sounds fine. I don't believe there's any need to delete/recreate the LUNs, though. If the VGs are okay, you don't even need to delete those -- you can just unmount, lvremove, and then recreate the lvols/fs that you want. I'm assuming you don't need any actual reformatting of these drives.

It sounds like you have a good grasp of things, but let me know if you want more details.

Mic

[jane zhang]

Hi,

Thanks for the reply.

The maximum number of LUNS is reached, So I do not need to delete all 8 LUNS and only recreate 5 or 6 to increase performance?

Some of the LUNS are created with smaller capacity, and my new file system will take more space, how to do with this?

If I do not do deletion and recreate the LUNS. Everything is clean?

Please confirm with this.

[A. Clay Stephenson]

The number of LUNS has very little to do with performance. The key is to retain as much unallocated space as possible so that your AutoRAID stays in RAID 1/0.

Use arraydsp -i to get the ArrayID

then to delete a LUN,
arraycfg -L LUN -d ArrayID where LUN is 0-7

to create a new LUN
arraycfg -L LUN -a size -V ArrayID where size is specified in MBytes

Man arraydsp, arraycfg for details.

Note that the 12H is a High-Voltage Differential (HVD) SCSI device only. Make certain that you use HVD SCSI controllers in your N box.

For best performance, allocate each volume group as 2 equally sized LUN's. LUNA's primary pathy should be through controller X (alternate Y) and LUNB's primary path should be through controller Y (alternate X). You then stripe each LVOL in this VG across both LUNs --- typically using a 64KB stripe size.
This will fully utilize both external SCSI busses and all four internal SCSI buses.

As I said earlier, leave as much space unused /unallocated as possible --- if you can stay under 50% allocation, all of the 12H will be RAID 1/0.

If you follow these rules, you will be pleasantly surprised at how well these old gals will perform.

[Mark Grossman]

jane,
we have 2 autoraid 12h running Oracle production for 4 years. As Clay states, unless you can keep 50% or so free disk you may have some performance issues as we have over the years. We offloaded Oracle DB redo/archive logs to jbod raid 1 sc10's with hpux mirrordisk and saw good improvement as our 12h's filled up.
Also, we saw some scsi lbolts in syslog for the 12'hs and had to set the pv timeout to 180 - for example:
pvchange -t 180 /dev/dsk/cxtxdx
We also went down to 2 big LUNS per 12H with no problem.
I agree the 12h's have been workhorses,but
if this is production though and speed is a major issue make sure to have lots of free disk space.
We are finally going to buy (i hope) an eva3000 fibre attached solution.

[jane zhang]

Hi Mic /Clay,

I am now wondering if it is necssary to delete LUNS and recreate them again if I have the option just do at LVM level ( vgexport then vgcreate and then /etc/fstab )and then just move new file over?

Please let me know if I can just do this.

As for performance, I saw all the LUNs are allocated.

Jane

[A. Clay Stephenson]

If you are after performance then ignoring them at the OS level does nothing. The key is to use the arraycfg commands to delete any LUN's that you don't actually need. The idea is to leave as much unallocated space as possible on the array itself.

[Mark Grossman]

Jane,
i agree with Clay - you must use the arraycfg method to deallocate and reallocate the luns. Just doing VG movement is not enough. The only way to free disk up and have it usable as raid1/0 is to reconfig the array. I believe once Autoraid 12H space is written to it becomes Raid5 forever even after files are deleted, unless arracfg is used to reset them.
Mark

[A. Clay Stephenson]

Actually the AutoRAID don't know nothing about no files deleted or otherwise. It don't know nothing about no filesystems neither. All it knows about are blocks within a LUN and unallocated space. Over time, if blocks are accessed infrequently and there are space constraints they are converted from RAID1/0 storage to RAID5. You are trading performance for space utilization. Frequently used blocks are migrated to RAID 1/0 but at all times at least 10% of the total array capacity is reserved as RAID 1/0. The user has absolutely no control over physical placement of data and the RAID1/0 <-> RAID5 migration occurs automatically and hence, the name "AutoRAID".