FAQ
Hello all,

I have inherited several Oracle 9.2.0.8 data warehouses on HP-UX 11.11 servers, each 2+ TBs. All of them are experiencing various performance issues.

The db_multiblock_read_count (MBRC) on these databases are explicitly set to the value of 8. To try to get a better idea of what we might increase the MBRC to, I wanted to figure out the values for the formula:

[stripe width] x [stripe size] / [db_block_size ]

How can I determine the values for stripe width and stripe size on HP-UX 11.11?

I thought perhaps the lvdisplay command might have the info. Looking at typical output, I see that there is a Stripe Size. Would Lv Size correspond to the stripe width?

$ lvdisplay /dev/vgdb/lvol1
--- Logical volumes ---

LV Name /dev/vgdb/lvol1
VG Name /dev/vgdb
LV Permission read/write
LV Status available/syncd
Mirror copies 0
Consistency Recovery MWC
Schedule striped
LV Size (Mbytes) 1198080
Current LE 4680
Allocated PE 4680
Stripes 6
Stripe Size (Kbytes) 1024
Bad block NONE
Allocation strict
IO Timeout (Seconds) default

I also looked at the vgdisplay command, part of which I have included below. Is there something here that is the equivalent of stripe size and stripe width?

Volume groups ---
VG Name /dev/vgdb
VG Write Access read/write
VG Status available, exclusive
Max LV 16
Cur LV 5
Open LV 5
Max PV 255
Cur PV 36
Act PV 36
Max PE per PV 65535
VGDA 72

PE Size (Mbytes) 256
Total PE 14364
Alloc PE 14364
Free PE 0
Total PVG 0
Total Spare PVs 0
Total Spare PVs in use 0

Logical volumes ---
LV Name /dev/vgdb/lvol1
LV Status available/syncd
LV Size (Mbytes) 1198080
Current LE 4680
Allocated PE 4680
Used PV 12
....
....

I realize that perhaps the best way to determine the optimal MBRC value with these file systesm would be to use the dd command and write a large datafile with different block size options to the filesystems. These database though have been up and running for quite a while and it's not possible to quiesce the systems and run benchmarks.

If anyone could confirm what I should be looking at with lgdisplay or vgdisplay, or can suggest another command, it would be greatly appreciated.

Thanks,
Lou Avrami

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postedSep 4, '08 at 8:49p
activeSep 4, '08 at 10:11p
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Greg Rahn: 1 post Lou Avrami: 1 post

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