Mailing List Archive

Paul,
It sounds like you are running the Crossroads router in "Fibre
Channel to SCSI Mapping Mode" of auto. Change the mode to "Indexed" and this
should fix your problem. The mapping mode determines how the targets behind
the router (i.e. tape that are attached to the SCSI side of the router) are
seen by Fibre Channel hosts on the network. Specifically, the various
addressing modes determine how Fibre Channel LUNs are mapped to the SCSI
peripherals on the router, and how that mapping can change when you reboot
or reconfigure the router.
You normally want to use indexed mode to ensure that particular target/luns
on the SCSI side of the router are persistently presented as the same LUNs
on the Fibre Channel side of the router, regardless of whether devices have
been removed on the SCSI side or were turned off when the router booted.
Mike


-----Original Message-----
From: Paul Caron [mailto:caron@sig.com]
Sent: Friday, November 01, 2002 11:02 AM
To: toasters@mathworks.com
Subject: Crossroads Problems


We are currently trying to implement a SAN backup solution involving
several F840 (ONTAP 6.2R2, latest FW) and R100 (ONTAP 6.2.1, latest FW)
filers, a Brocade Silkwork 3800 switch (kernel 5.3.1, fabric OS 3.0), a
Crossroads 10000, an ATL P7000 tape drive library with 8 SDLT drives, and
Commvault Galaxy software (4.1.0, Build 26). We have tried firmware
versions 4.03.16, 4.03.17, and 4.19 on the Crossroads 10000.

The problem we are experiencing is that the devices on our filers which
represent the SAN attached tape drives (shown by sysconfig -t) get randomly
recreated every time the Crossroads reboots. Since we can't guarantee
which devices will get assigned to which tape drive LUN, they often do not
match those configured in the Commvault Galaxy backup software. The
resulting mismatch causes many backup problems. It appears as though the
Crossroads is not presenting the tape drives available on the ATL P7000 in
the same order every time it reboots.

We have read through the information available at
http://www.netapp.com/osn/info/config.html#fcsan. This site shows support
for the Brocade 3800. Although they do not call out support for the
Crossroads 10000 specifically, they do show a wide range of options using
various SCSI-FIBER bridges with a variety of libraries. The StorageTek
library they show uses a Crossroads 42xx series switch.

Has anyone else run into this situation? Is there any way of compensating
for this on the Netapp filers? I realize that it would be better if the
Crossroads would present the tape drive LUNs in the same order every time,
but that doesn't appear to be configurable. It would help if we could
permanently assign the devices to the tape drive LUNs on the filers.

BTW, we have received suggestions regarding using the Netapp "storage
alias" and "storage unalias" commands. However, since the Galaxy backup
software relies on the actual device names (i.e. rst0l, nrst0l, urst0l,
etc.) this hasn't helped us so far.

Paul Caron <caron@sig.com> writes:

> The problem we are experiencing is that the devices on our filers which
> represent the SAN attached tape drives (shown by sysconfig -t) get randomly
> recreated every time the Crossroads reboots.

This was a problem that I encountered early in ONTAP 6.0.x (and 6.1.x
to?) although sporadic, often enough to write a perl script to reset
the tape aliases a few times a week.

The LUN did not change, but the filers decided to rename the the
aliases after the fc-card was reset or unplugged from the Brocade.
(The last was a precautionary action to prevent the filer from
panic'ing from a SCSI reset when the bridge or library was rebooted)

> It appears as though the Crossroads is not presenting the tape
> drives available on the ATL P7000 in the same order every time it
> reboots.

Although I am using the STK (Crossroad) 3250, I would believe that the
menus/commands are similiar.

Have you set any values in the "Fibre Channel to SCSI mapping"/
"Mapping Table# ??
Does the values change after reboot?
What about "Display Attached SCSI Devices", does this change between reboots?

> Has anyone else run into this situation? Is there any way of compensating
> for this on the Netapp filers?

Without the Crossroads not keeping the LUN values stable, you are out
of luck. As far as I know there is no way of keeping track of a
changing LUN.

>
> BTW, we have received suggestions regarding using the Netapp "storage
> alias" and "storage unalias" commands. However, since the Galaxy backup
> software relies on the actual device names (i.e. rst0l, nrst0l, urst0l,
> etc.) this hasn't helped us so far.

The Filer actually sees the real LUN value, but you may assign an
alias, such as st01 st02 ... the device names rst02,nrst02,urst02 etc
gives the device functionality.

To sum up: If the Crossroads keep changing the LUN values, I would
suggest you bring your vendor to bring this case directly to
Crossroads.

>>>>>>>>>>>>>>>>>>>.rune
--
Rune Bakken
Senior System Administrator
Telenor Business Solutions (Nextra), ManagedServices/*/IP-Services
Ph: +47 992 86 474

Thanks for your responses. Here are some answers to the questions that were
presented.

> Have you set any values in the "Fibre Channel to SCSI mapping"/ "Mapping
Table#"?

We have a custom map that we're using to map the individual tape drives to
Crossroad LUNs.

> Do the values change after reboot?

No.

> What about "Display Attached SCSI Devices", does this change between
reboots?

No. The attached SCSI devices are always the same.

----------------------------------

The "Fibre Channel to SCSI Mapping Mode" for our Crossroads is not set to
auto. We are using a custom map to make sure that each tape drive always
has the same LUN. We are not using the "index" map since that one is
currently being used for our Windows media agent. However, there doesn't
appear to be a difference between custom maps and the "index" map other than
the name of the "index" map cannot be changed. If I am mistaken, please let
me know.

Also, I guess I need to qualify my details a bit more. The LUNs presented
by the Crossroads are fixed in that they are always refer to the same drive
on the P7000. The problem is that the LUNs get assigned to different
devices on the filer. For example, LUN 2 will be assigned to the rst1l,
nrst1l, ..., urst1a devices after one of the Crossroads reboots. After
another Crossroads reboot, LUN 3 will be assigned to those same devices on
the filer. We need to preserve a consistent device mapping on the filer.

Reassigning storage aliases seems to be the best workaround we've found so
far. My quick hack script to do this is below (the x:xxx:xxxxxx:xxxxxx
represents the WWN of the Crossroads). We're still looking for a better
long term approach. Either the Crossroads needs to present the LUNs in the
same order every time, or the Netapp filer needs to have a way to specify a
persistent device-to-LUN mapping for FCAL attached devices.

-----------------------------------------------------------------------
#!/bin/sh

FILER=$1

if [ -z "$FILER" ]; then
echo "usage: resetaliases <filername>"
exit 1
fi

/bin/rsh $FILER storage unalias -a
/bin/rsh $FILER storage alias mc0 WWN[x:xxx:xxxxxx:xxxxxx]
/bin/rsh $FILER storage alias st0 WWN[x:xxx:xxxxxx:xxxxxx]L1
/bin/rsh $FILER storage alias st1 WWN[x:xxx:xxxxxx:xxxxxx]L2
/bin/rsh $FILER storage alias st2 WWN[x:xxx:xxxxxx:xxxxxx]L3
/bin/rsh $FILER storage alias st3 WWN[x:xxx:xxxxxx:xxxxxx]L4
/bin/rsh $FILER storage alias st4 WWN[x:xxx:xxxxxx:xxxxxx]L5
/bin/rsh $FILER storage alias st5 WWN[x:xxx:xxxxxx:xxxxxx]L6
/bin/rsh $FILER storage alias st6 WWN[x:xxx:xxxxxx:xxxxxx]L7
/bin/rsh $FILER storage alias st7 WWN[x:xxx:xxxxxx:xxxxxx]L8

exit 0

-----------------------------------------------------------------------