TJohnson-LCSD Absent Member.
Absent Member.
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Persistent iSCSI Device Names

I am setting up a new SLES10SP2/OES2SP1 2 node cluster using iSCSI shared storage
and NCS.

My SBD LUN on the iSCSI SAN showed up as /dev/sda and my other iSCSI LUN is
/dev/sdb on both boxes. I applied some updates on the servers, rebooted and now I see the SBD LUN on 1 server is /dev/sdb and on the other server it is /dev/sda, I
reboot first server and the SBD LUN is back on /dev/sda

I have never seen this happen with any of my other iSCSI LUNs but it has me
thinking if it will happen again and what kind of havoc will it wreak on my
cluster. So my question, is there a way to "pin" a device name (/dev/sda,
/dev/sdb, etc.) to a certain LUN and/or is there a way to use /dev/by-id
for iSCSI?

I have done some searches ban found some info on using udev to accomplish
this but I am not sure if that is the way to go?
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4 Replies
utman Absent Member.
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Re: Persistent iSCSI Device Names

I would recommend using the /dev/disk/by-id or /by-name. They will remain constant across reboots while the SCSI notation may change after a reboot.
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TJohnson-LCSD Absent Member.
Absent Member.

Re: Persistent iSCSI Device Names

I am a novice when it comes to setting up the disk-by-id or disk-by-name. I do not see these in my /etc./fstab only in partitioner or fdisk, however, i have not setup the disks in OES, no initilization, no FS, etc.

Any help in how to proceed would be greatly appreciated.
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utman Absent Member.
Absent Member.

Re: Persistent iSCSI Device Names

You don't need to set it up, udev does that for you. Simply go to /dev/disk/by-id or /by-name and look at the devices. Determine which device maps to the /dev/sdb device you want and then use /dev/disk/by-id/xxxxx inplace of /dev/sdb.
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TJohnson-LCSD Absent Member.
Absent Member.

Re: Persistent iSCSI Device Names

utman,

Thanks for the info, my confusion was in thinking that I had to ensure persistent device names for iSCSI LUNs when setting up Novell Clustering Services. After talking with Novell, i realized that when creating cluster resources EVMS is used so the resource points to a /dev/evms device so any changes in the /dev/sdx device name for the iSCSI LUN is not an issue.

This also applies to POSIX resources when using evms but if evms or lvm is not used then you would have to replace /dev/sdx with something from /dev/disk/by-id

File this under the DUH category for me. Thanks for your help.

Tim
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