On 08/18/2009 01:47 PM, Auld, Brian (LeftHand Networks) wrote:
I have a question about the lifetime of volume/disk info for SAN
disks.
Say my server has discovered a disk/volume on a SAN (iscsi or fc). A
connection is established at the transport layer. Presumably disk
information (eg. vpd inquiry data and the like) is saved in a layer
(SBC disk layer?) above the transport.
The scsi layer has info on the disk. Some of it is in /sys/block/sdX/device.
What happens if the server explicitly logs out of the session for the
above disk/volume using whatever initiator tools are available to
them? Does the disk/volume info remain for some time in the higher
layer(s) or do all the data structures related to that disk/volume
get unplugged/removed when the transport connection is taken away?
Of course, it goes without saying that no other objects in the OS
(files, devices, mountpoints) are using the disk when the logout
occurs.
For iscsi, if you logged out of the session with a tool like iscsiadm
then the disks would be removed from the OS.
Same goes for FC I guess. If you were to remove the fc module like lpfc
or qla2xxx then the hba, ports and disks would go away. I am not sure if
there is a tool that allows you to remove just one port (for a vport you
can use the sysfs interface though).
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