Very Computer

by **Edo** » Fri, 26 Mar 1999 04:00:00

Should the number of VGs be kept to a minimum? Is there any benefits in
having few jfslogs on the system.
--
Edward Dixon
Senior Consultant
Coda Consulting
Open Systems Services and Support.

by **Flemming Josephse** » Fri, 26 Mar 1999 04:00:00

Can't see why you would want to limit the number for technical reasons.
Have as many or as few as you like. Mind that, in AIX versions prior to
4.3.2, you can only have 32 physical devices in a volume group.

JFS logs can be very very very busy and you may benefit from have more
than one per volume group. And in some cases you may benefit from
distributing over as many controllers and disks as possible.

Suggested reading: AIX storage management (publication # GG24-4484-00)

You can get this at www.redbooks.ibm.com

> Should the number of VGs be kept to a minimum? Is there any benefits in
> having few jfslogs on the system.
> --
> Edward Dixon
> Senior Consultant
> Coda Consulting
> Open Systems Services and Support.

by **Bob Shai** » Sat, 27 Mar 1999 04:00:00

> Should the number of VGs be kept to a minimum? Is there any benefits in
> having few jfslogs on the system.
> --

In AIX's LVM implementation, the VG is the logical unit of recovery.
Having few VG's implies:
1) more contention for jfslog (not usually a problem since only
metadata is logged)
2) more data to be reloaded, possibly backleveled when there's
a media failure on any disk in the volume group.

Having many VG's breaks up the free disk space (FREE PPs) into many
clumps, leaving you less flexibility in expanding filesystems as
required.

I recommend at least 2 VGs for any system beyond single-user
workstations .... rootvg, uservg.

Beyond that it's application dependent.

--

Open Systems Specialist Champaign, Illinois
/* Opinions expressed are mine... go get your own! */

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