OpenVMS Backup and SAN best practices

[Kel_Boyer]

I'm unable to find a definitive answer for this elsewhere, so I'm hoping that I can get steered in the right direction here.

Does HP recommend specifically throttling OpenVMS Backup to a DIOLM of 8 when performing backup to a Fibre Channel SAN device? I know there was talk of patching the Backup image to only do 8 IO at a time to allow SAN arrays like the EVA to better handle the concurrent requests.

I am not able to find a reference to it in a recent patch, however.

My understanding of the correct best practice is that heavy concurrent IO applications should be throttled to avoid FC port queues, but again, I am not able to find a place where this is documented specifically.

I would also be very interested in reading anything that HP has for best practices regarding EVA Continuous Access and OpenVMS backup on the same SAN.

Thanks!

[Wim Van den Wyngaert · Accepted solution]

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&taskId=110&prodSeriesId=459922&prodTypeId=18964&prodSeriesId=459922&objectID=c00709946 ?

With the SAN Cache, high DIOLM causes memory thrashing. HP recommends to reducing DIOLM to 32.

Wim

[Richard Brodie_1]

There's the IO_LOAD qualifier in BACKUP in 8.3,
and I believe there were backports.

[Kel_Boyer]

Thanks. I appreciate the responses.

[Kel_Boyer]

HP's standard recommendation for DIOLM in conjunction with an EVA on a SAN is to reduce the DIOLM to 32.

[Clark Powell]

We have tried to duplicate this problem and have had no success according to this test given to us by HP:

$set term/wid=132
$ana/sys
SDA> fc stdt/all ! for all adaptors - look for values in QF seen and SEQ TMO
if this test is correct we only see 6 instances in 50 to 100 days of operation (and backups)

As for setting the DIOLM low sometimes this is a lot of work as for example, DECwindows might decide on boot to run autogen and reboot again because it doesn't like DIOLM set to 32. In OpenVMS 8.3 and 7.3-2 with patches HP created another solution:

Using the wtid limits available in vms732_fibre_scsi-v0400 to set
up a maximum number of io credits to the port. The suggested values for
different FC controllers are:
HSG80 240/(number of hosts + 2)
EMA12000 "
EMA16000 "
ESA10000 "
ESA12000 "
MSA1000 512/(num hosts+2)
MSA1500 "
EVA GL (3000 and 5000) 80
EVA XL (4K, 6K, & 8K) at least 80
XP128/512/1024 16
XP12000/10000 16

To set a cap on OpenVMS v7.3-2 with vms732_fibre_scsi-v0400 (or
later) installed use the following:

$ana/sys
SDA> fc show wtid ! to get the wwid
! use the host address to set for all ports on a controller
SDA> fc set wtid/wwid=/cap=
SDA>exit
The SDA set wtid commands should be added to a command procedure and executed in systartup_vms.com so they are activated for every boot.

I would contact the storage group to see if they agree with this solution still because we simply haven't needed to use (and test) it.

Clark Powell

[Tom O'Toole]

You would set DIOLM on the backup accounts, not systemwide.