There are known issues and limitations with the SAN Volume Controller and
an IBM® System p® AIX® host.
The AIX host imposes
the following size limitations on disk volume sizes:
- 1 TB
- On 32-bit AIX platforms
(4.3.3, 5.1, 5.2, or 5.3)
- 2 TB
- On 64-bit AIX 5.1 platforms
(1 TB for anything reliant on bootinfo)
- 2 TB
- On 64-bit AIX 5.2 platforms
(2 TB when using LVM bad block relocation)
- 2 TB
- On 64-bit AIX 5.3 platforms
- 2 TB
- On AIX 6.1 platforms
The following
IBM support
Web site provides for the most current information about known restrictions:
www.ibm.com/storage/support/2145
On
a heavily loaded system, you might see the following symptoms, which
can indicate that the host is low on direct memory access (DMA) resources:
- You might see errors that indicate that the host bus adapter (HBA)
was unable to activate an I/O request on the first attempt.
- You might see lower-than-expected performance with no errors being
logged.
To reduce the incidence of these messages, you can increase
the resources by modifying the maximum transfer size attribute for
the adapter as follows:
- Type the following command to view the current setting:
lsattr -El HBA -a max_xfer_size
where HBA is
the name of the adapter logging the error. For this example, the HBA
is fcs0.
- Type the following command to increase the size of the setting:
chdev -l fcs0 -P -a max_xfer_size=0x1000000
Note: To
view the range of allowable values for the attribute, type: lsattr
-Rl fcs0 -a max_xfer_size
- Restart the host to put these changes into effect.