Newbie scsi question

Justin C. Sherrill justin at
Wed May 3 06:29:02 PDT 2006

On Wed, May 3, 2006 6:39 am, Karthik Subramanian wrote:

> Consider a typical SAN setup - an FC switch with a couple of JBOD's
> and a couple of machines hooked up to the switch.
> On linux, the disks from the JBOD are recognised as /dev/sd[a-n]. The
> hitch is that the device naming is not consistent across reboots; the
> first time around, /dev/sdb could refer to the first disk on the JBOD.
> The second time around, you don't know what it points to, as the
> assignment of device names to disks depends on the order in which the
> disks are recognised at boot time. Of course, there are fixes to this
> problem - like devlabel/udev, but they are essentially fixes to a
> problem that should never have been there in the first place.

I've never had a fibre channel setup, so I can't confirm this, but at
least with IDE drives, I've thought the position of the disk determined
the device name - the first disk on the first controller is ad0, the
second is ad1, the first on the second controller is ad2, etc.  It could
be coincidence.

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