how to tune disk bottleneck of XP256

[Ming Zhao]

In our system(N4000-440, 5 cpu, 4G physical memory, HPUX11.0, SAP, Oracle, Fibre channel and XP256 with 4G cache and 384M share memory, all data filesystem are P-VOL of CA, all LDEV are RAID5)has following parameters:

dbc_min_pct = 5
dbc_max_pct = 10
bufpages = 0
nbuf = 0
swapmem_on = 1

When I run glance, the disk utilization is always 100% busy during peak period, %wio is 60.

My questions are:
1. how to tune disk performance?
2. If I incease dbc_max_pct to 15, is it helpful?

Thanks,

[Michael Tully]

Hi,

Before attempting to change any kernel
parameters you probably need to identify
why disk is 100% utilised and which
disk(s) are reporting it. First off try
running 'sar -d 5 5' during this peak or
use glance and select I/O by disk. Then
you will be able to determine what lies
on that disk that could causing a problem.

-Michael

[Thierry Poels_1]

Hi,

did you check your Oracle buffer hit ratio?? Increasing db_buffers might do wonders.

regards,
Thierry.

[Thierry Poels_1]

ooops typo:
db_block_buffers of course