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Current limitations when using iSCSI software initiator
The code available at the time of preparing this book had limitations when using the iSCSI
software initiator in AIX. These restrictions will be lifted over time:
򐂰 Single path only is supported.
򐂰 Remote boot is not supported.
򐂰 The maximum number of configured LUNs tested using the iSCSI software initiator is 128
per iSCSI target. The software initiator uses a single TCP connection for each iSCSI
target (one connection per iSCSI session). This TCP connection is shared among all
LUNs that are configured for a target. The software initiator’s TCP socket send and
receive space are both set to the system socket buffer maximum. The maximum is set by
the sb_max network option. The default is 1 MB.
Volume Groups
To avoid configuration problems and error log entries when you create Volume Groups using
iSCSI devices, follow these guidelines:
򐂰 Configure Volume Groups that are created using iSCSI devices to be in an inactive state
after reboot. After the iSCSI devices are configured, manually activate the iSCSI-backed
Volume Groups. Then, mount any associated file systems.
Note: Volume Groups are activated during a different boot phase than the iSCSI
software driver. For this reason, it is not possible to activate iSCSI Volume Groups
during the boot process
򐂰 Do not span Volume Groups across non-iSCSI devices.
I/O failures
To avoid I/O failures, consider these recommendations:
򐂰 If connectivity to iSCSI target devices is lost, I/O failures occur. To prevent I/O failures and
file system corruption, stop all I/O activity and unmount iSCSI-backed file systems before
doing anything that will cause long term loss of connectivity to the active iSCSI targets.
򐂰 If a loss of connectivity to iSCSI targets occurs while applications are attempting I/O
activities with iSCSI devices, I/O errors will eventually occur. It might not be possible to
unmount iSCSI-backed file systems, because the underlying iSCSI device stays busy.
򐂰 File system maintenance must be performed if I/O failures occur due to loss of
connectivity to active iSCSI targets. To do file system maintenance, run the fsck
command against the effected file systems.
Chapter 8. AIX host connectivity
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