Re: [linux-iscsi-users] Device reordering on iscsi restart

[Andrew D. <ad...@tr...>]

On Thu, 14 May 2009, Mike Christie wrote:

> The scsi layer will hand out the sdX names to the first driver requesting 
> them, so if you load drivers in different order or add targets in different 
> order (iscsid will scan multiple targets in parrallel so this can happen 
> pretty easily) you will have different sdX on each reboot or restart of the 
> iscsi driver.

Figures. That's an issue for many people I imagine.

> Do you care what path you use? I think in RHEL 4 udev is partially suported 
> for this. You can write a rule to name the iscsi disk using scsi_id or using 
> the target and portal info (look in /etc/udev). I think if you look in 
> /dev/disk it might do some of this by default already. But if there are two 
> paths to the same disk then they both get the same name sometimes.

Yes and no. We really want to firewall the Sun machine so iSCSI only 
appears on our SAN VLAN, leaving HTTP/FTP on our mail VLAN. But that's 
not done yet (maybe through the Solaris CLI - we can't find it in the 
GUI, but Sun issues warnings about warranty voidance if you mess with 
things; it's supposed to be an appliance managed via the web). So if we 
do that, one IQN will disappear. We'd prefer the one we aren't using to 
disappear :-)

I hadn't been aware of udev (invented since I started with Linux) but 
others mentioned it. RHEL5 seems to have a rich set in /dev/disk/by-path/ 
showing up in udevinfo, but RHEL4 does not - only some entries for 
direct-connected disks. "udevinfo -q all -p /block/sdc/sdc1" on RHEL4 
shows only the basic mode and owner info, not the extended and symlink 
info. So I guess it's disk labels for RHEL4

I note that RHEL5 switched to iscsiadm (maybe open-iscsi from 
iscsi-linux) and while in RHEL4 I found the iSCSI /dev/sdx with "iscsi-ls -l",
in RHEL5 I can't find that information. I saw it in syslog. As I had 
already made a partition and disk label in RHEL4, "mount -L" worked 
anyway.
I didn't see that it got automounted by hotplug like a USB stick does.

-- 
Andrew Daviel, TRIUMF, Canada
Tel. +1 (604) 222-7376  (Pacific Time)
Network Security Manager