Re: Linux Cluster using shared scsi

From: James Bottomley (James.Bottomley@SteelEye.com)
Date: Thu May 03 2001 - 08:52:03 EST


There is another nasty in multi-port arrays that I should perhaps point out:
a bus reset isn't supposed to drop the reservation if it was taken on another
port. A device or LUN reset will drop reservations on all ports. This
behaviour, although clearly mandated by the SCSI-3-SPC, is rather patchily
implemented in arrays and I have seen some multi-port arrays that will,
illegally, drop reservations on all ports on receipt of a bus reset.

Unfortunately, most Linux SCSI drivers won't issue device resets on command,
they'll only issue bus resets, so it is possible to get into a situation where
you cannot break a reservation belonging to a dead machine, if you set up a
point-to-point cluster rather than a true shared-scsi one.

James

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