> Sorry if this has been covered here in the past. Searches of
> various linux mlists for "multi|initiator|reserve|release" failed to
> turn up anything (recent) that looked particularly related, so here goes...
>
> There's been some recent discussion and questions 'round here
> about multi-initiator setups on linux. From what I can determine,
> the linux scsi mid-layer doesn't do any sort of RESERVE / RELEASE
> stuff. (RESERVE_10, RELEASE_10 weren't even defined in
> <scsi/scsi.h> until very recently).
You can still issue the RESERVE/RELEASE command using the sg driver via the
read/write interface or though the ioctl SCSI_IOCTL_SEND_COMMAND.
HOWEVER, once you issue the RESERVE Linux does not do very well handling the
RESERVATION CONFLICT on the other systems - they reset the bus. Sort of
defeats the purpose of the reservation. On the other hand there is no
interface to reset the device or bus to clear the reservation in case of a
failed system so this bug comes in handy.
There is work afoot to fix the bug and provide an interface to issue a Bus
and/or device reset.
>
> So with two or three linux systems attached to the same fibre channel
> (loop in this case:-), I can mount the same target (ext2 f.s.) from
> any+all the systems and (blindly+) merrily work away...
> while eventual multiple writes clobber the file system, right?
Yep, you really need to either restrict access to the file system through
something like RESERVE/RELEASE or use a cluster file system (which does not
exist yet that I know of).
Eddie Williams
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