Performance versus Size - VG

[Tony Willis_1]

My formal LVM training came prior to 11
and JFS. Therfore, I understand that "rukes" chang.
Notes that I have suggest that a VG should not exceed
64GB on EMC Symmetrix, Hitachi, or Symbios
DISK SYSTEMS, due to "Performance" degradation.

My DFA is asking if, I can give him a 128GB VG.
I physically can, BUT, is it better to create TWO
64GB VGs? Mount Point is not an issue.

I have found nothing in print to justify my note.

[Dave Wherry]

I currently have 4 volume groups that are each around 70GB and I have not noticed any problems with performance. I'm actually trying to migrate all of this data to fewer, larger volume groups as I think it is easier to manage. I wanted to do this when I built the system, but, we had trouble creating the logical volumes and had to create smaller volume groups just to finish on time. That was related to extent stripping and have since gotten past that.
I can't direct you to anything in print that will confirm this. I have discussed it with my HP A.S.E. and he blessed it.

[Bruce Regittko_1]

Hi,

I doubt that the size of the volume group alone would contribute significantly to performance degradation, although I also haven't seen anything in print to confirm this.

Keeping the physical extents defragmented and stripping should improve performance more than anything else.

--Bruce

[thinphony]

Hi!
You may need to increase the Physical Extent size when creating 128GB VGs, I think no performance problems, but it may have low disk utilization rate.

thinphony Qu.

[Dan Zucker]

In general I have not seen problems with large VGs and I have 140giga, and 115giga VGs. I have seen problems with using RAID5. The writing is very slow, but reading does not seem to be a problem.
By slow I have backed up 20LVs in one VG in 5 hours, the restore was 24 hours.

You should take into consideration the backup/restore product your using and if there are limitations.

[Carol Garrett]

We have some 128GB VGs and dont notice any performance problems. Its not the size of the VG which counts - it simply keeps track of info on its lvols, its the size of the lvols which are important. Weve tried 64Gb or 128Gb lvols, dont see any real performance differences, except ensure the larger the lvol the more controllers and disks you stripe it over - to keep i/o data transfer rates as high as possible.

[Tony Willis_1]

I have read all the reply state,emts.

I thak all of you.
Best points were - Backup/restore, extent size, and lvol size.

This is the result:
1. Dual fiber channel connections.
2. 4 stripped disk [er volumn
3. 4 volumns per group
4. 6vg

In 1980 it was loading BL unix on 20MB drives.
Today it is deciding how to dice up .5TB

I appreciate the input., points to all.