SUMMARY: Raid Manager with Veritas

Date: Thu Nov 18 1999 - 07:45:33 CST

I got a couple of responses on this, and also logged a call with Sun. The
original question is at the end.

Thanks toTimothy Lindgren for the following;

There is a performance hit, but it's minimal. VM will automatically set it's I/O
at boot time to optimal SCSI settings. The biggest hit you'll take is with the
SCSI limitations of 128k blocks. You can tune this with /etc/system to increase
I/O performance. With the RSM2000 it;s best to open up SCSI a bit, and let the
raid controller handle any i/o splits.

* Open up SCSI
set maxphys=8388608
set ufs:ufs_HW=8388608
set ufs:ufs_LW=6291456

* Volume Manager support.
set vxio:vol_maxioctl=131072
set vxio:vol_maxspecialio=10240
set vxio:vol_maxio=10240
set vxio:voliomem_max_memory=12582912
set vxio:voliomem_kvmap_size=15728640
set vxio:voliomem_base_memory=1048576

* VxFS support to move from 8k stack to 16k.
set lwp_default_stksize=0x4000
set rpcmod:svc_run_stksize=0x4000

and to Mark Neill for this;

     The hardware raid in the RSM is beter than Veritas's software raid.
However, Veritas File System give a better performance than UFS.

     I don't have any numbers to support it, but I would think smaller
RSM LUNS concatted through Veritas would be, at the very least, more
managable, allowing you a better ability to move busy disks around and such.

Sun said that it is a good idea to run Veritas over Raid Manager. In reality it
shouldn't make much difference whether I use one large Lun or several smaller
ones, but I tend to agree with Mark that smaller ones will be more manageable.

One interesting point that Sun mentioned was that if the system was altered to
support more Luns, the boot time could alter from say 30 minutes up to 2 / 3
hours as the devices could only be detected by timing out.

Original question
I have a system that I am now able to reconfigure from Sol 2.5.1 to Sol 2.6 - an
E4000 with RSM 2000 arrays using 21 9Gb drives

The drives were originally configured as 4 luns under Raid Manager, then split
into subdisks/volumes as required by running Veritas over that. As far as I can
tell, the original idea was to purchase more disk which meant they would soon
meet the limitation of 8 lun support for Raid Manager in 2.5.1, so Veritas was
bought as well.
The luns are RAID 5, and the Veritas volumes are single concats.

Is anyone aware of any overheads or performance issues that are produced by
running Veritas over Raid Manger, and would it be better, for example, to
     1) smaller luns, run Veitas and configure the volumes as required.
     2) large luns, and partition them as required to replicate the veritas
volumes which means I can remove Veritas.

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