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OpenVMS Backup and SAN best practices

 
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Kel_Boyer
Occasional Contributor

OpenVMS Backup and SAN best practices

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!
6 REPLIES 6
Wim Van den Wyngaert
Honored Contributor
Solution

Re: OpenVMS Backup and SAN best practices

Richard Brodie_1
Honored Contributor

Re: OpenVMS Backup and SAN best practices

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

Re: OpenVMS Backup and SAN best practices

Thanks. I appreciate the responses.
Kel_Boyer
Occasional Contributor

Re: OpenVMS Backup and SAN best practices

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

Re: OpenVMS Backup and SAN best practices

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
Respected Contributor

Re: OpenVMS Backup and SAN best practices


You would set DIOLM on the backup accounts, not systemwide.
Can you imagine if we used PCs to manage our enterprise systems? ... oops.