From: Bigby <bi...@sh...> - 2013-01-17 14:22:11
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Hello again at initiator side (open-iscsi) I need to guarantee a fixed WWN for a certain scst device (which is currently coming from /dev/vdb at scst side but in the future might be /dev/vdc, or /dev/sdb or whatever... ). That WWN must never change even if I change the LU-Number, add additional devices to the target, change the backing "filename" or something like that . In other words, I want to decide which exported LU gets a certain WWN. The WWN I am seeing from client side seems a hash of something, and the scst manual is not 100% clear on which factors contribute to such hash . I have found this doc of 2010 https://lkml.org/lkml/2010/9/14/197 which says that it depends on a module parameter (ok I will not change that value) and from a seemingly random value which is generated at device creation time and is probably made persistent by writing it somewhere (where?) ... ok I would like to prevent random things made persistent out of my control so I would like to override that... My scst.conf is like this: -------------- HANDLER vdisk_blockio { DEVICE mydisk1 { filename /dev/vdb t10_dev_id "myid1" } } ..... TARGET_DRIVER iscsi { enabled 1 TARGET {...... .....} } -------------- by specifying the t10_dev_id manually like above inside the device "mydisk1", is it guaranteed that the WWN will always stay the same for "mydisk1" even after reconfigurations of other parts of scst.conf ? Thank you B. |
From: Bart V. A. <bva...@ac...> - 2013-01-17 16:32:27
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On 01/17/13 15:22, Bigby wrote: > at initiator side (open-iscsi) I need to guarantee a fixed WWN for a > certain scst device (which is currently coming from /dev/vdb at scst > side but in the future might be /dev/vdc, or /dev/sdb or whatever... ). > That WWN must never change even if I change the LU-Number, add > additional devices to the target, change the backing "filename" or > something like that . In other words, I want to decide which exported LU > gets a certain WWN. > > The WWN I am seeing from client side seems a hash of something, and the > scst manual is not 100% clear on which factors contribute to such hash . > I have found this doc of 2010 https://lkml.org/lkml/2010/9/14/197 which > says that it depends on a module parameter (ok I will not change that > value) and from a seemingly random value which is generated at device > creation time and is probably made persistent by writing it somewhere > (where?) ... ok I would like to prevent random things made persistent > out of my control so I would like to override that... > > My scst.conf is like this: > > -------------- > HANDLER vdisk_blockio { > DEVICE mydisk1 { > filename /dev/vdb > t10_dev_id "myid1" > } > } > ..... > TARGET_DRIVER iscsi { > enabled 1 > TARGET {...... > .....} > } > -------------- > > by specifying the t10_dev_id manually like above inside the device > "mydisk1", is it guaranteed that the WWN will always stay the same for > "mydisk1" even after reconfigurations of other parts of scst.conf ? If you set the t10_dev_id explicitly in scst.conf then you are safe - the first eight characters of that ID are what is communicated to the initiator as the SCSI ID of that LUN. On the initiator side, /lib/udev/scsi_id will use these first eight characters, encode these in hex, prepend a "2" and will use that as the SCSI ID. The "setup_id" parameter only influences the t10_dev_id if it has not been specified explicitly in scst.conf. Bart. |