From: Jean Louis Di Domenico (jl.didomenico@HDS.COM)
Date: Wed Sep 18 2002 - 20:34:02 EDT
I need a simple help on this one. I have a doco added here-in.
I went to the WEB site archieve and did not manage to find anything.
I need to know:
1. Is it still current ?
2. Was it part of a cookbook or any IBM manual ?
3. Any comments from you would be welcomed.
Best Regards,
Jean-Louis, Sydney, Australia.
From: Matthew E Landt/Austin/IBM@IBMUS
Subject: Queue_depth
The current documentation states that the queue_depth limitations are:
queue_depth <= 32/LUN (disk)
queue_depth <= 256/port
For AIX the maximum number of LUNs presented to a port is 128...
Thus for a single server with max disk, a queue_depth of 2 is the maximum
allowable value.
The queue_depth should be the power of 2 value that does NOT exceed either
requirement.
This means that if the RAID-box has presented 128 LUNS to one port, and
there are 32 HBAs attached to that port and are SHARING all 128 devices, the
queue_depth must be 256/128/32 = 0.0625.
The highest power of 2 that does not violate the above rules is 0.
Therefor the maximum queue_depth for this environment is 0!
This is true for both single server with multiple HBAs/port or multiple
servers/port.
Max Queue_depths if all HBAs see all disks on a port
|---------------+---------------+---------------+---------------+-----------
----+---------------+---------------|
| Luns/Port | 1 HBA/port | 2 HBA/port | 4 HBA/port | 8
HBA/port | 16 HBA/port | 32 HBA/port |
|---------------+---------------+---------------+---------------+-----------
----+---------------+---------------|
| 1 | 32 | 32 | 32 | 32
| 16 | 8 |
|---------------+---------------+---------------+---------------+-----------
----+---------------+---------------|
| 2 | 32 | 32 | 32 | 16
| 8 | 4 |
|---------------+---------------+---------------+---------------+-----------
----+---------------+---------------|
| 4 | 32 | 32 | 16 | 8
| 4 | 2 |
|---------------+---------------+---------------+---------------+-----------
----+---------------+---------------|
| 8 | 32 | 16 | 8 | 4
| 2 | 1 |
|---------------+---------------+---------------+---------------+-----------
----+---------------+---------------|
| 16 | 16 | 8 | 4 | 2
| 1 | 0 |
|---------------+---------------+---------------+---------------+-----------
----+---------------+---------------|
| 32 | 8 | 4 | 2 | 1
| 0 | 0 |
|---------------+---------------+---------------+---------------+-----------
----+---------------+---------------|
| 64 | 4 | 2 | 1 | 0
| 0 | 0 |
|---------------+---------------+---------------+---------------+-----------
----+---------------+---------------|
| 128 | 2 | 1 | 0 | 0
| 0 | 0 |
|---------------+---------------+---------------+---------------+-----------
----+---------------+---------------|
- Matt Landt - Matthew Landt - Bldg 902 04-021F - 1-512-838-1327 - T/L
678-1327
This archive was generated by hypermail 2.1.7 : Wed Apr 09 2008 - 22:16:12 EDT