IBM TotalStorage DS300, Best Practices Manual, Page: 444 / 680

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IBM TotalStorage DS300 and DS400 Best Practices Guide
Multipath devices now show up under /dev/disk/by-name/. With multipath -l it is
possible to query the current path states.
Example 7-11 multipath device information and mounting
danube:~ # ls -l /dev/disk/by-name/
total 0
drwxr-xr-x 2 root root 88 Aug 3 11:33 .
drwxr-xr-x 5 root root 120 Jul 26 20:21 ..
lrwxrwxrwx 1 root root 10 Aug 3 11:33 20003390012f2c829 -> ../../dm-0
danube:~ # multipath -l
20003390012f2c829
[size=97 GB][features="1 queue_if_no_path"][hwhandler="0"]
\_ round-robin 0 [active][best]
\_ 3:0:2:0 sdb 8:16 [active]
\_ round-robin 0 [enabled]
\_ 3:1:2:0 sdc 8:32 [active]
danube:~ #
A filesystem can now be created on the device. Then the filesystem can be
mounted.
Example 7-12 creating filesystem
danube:~ # mkfs.reiserfs /dev/disk/by-name/20003390012f2c829
mkfs.reiserfs 3.6.19 (2003 www.namesys.com)
[...]
ReiserFS is successfully created on /dev/disk/by-name/20003390012f2c829.
danube:~ # mkdir /mnt/danube-disk1
danube:~ # mount /dev/disk/by-name/20003390012f2c829 /mnt/danube-disk1/
danube:~ # df -h /mnt/danube-disk1/
Filesystem Size Used Avail Use% Mounted on
/dev/dm-0 98G 33M 98G 1% /mnt/danube-disk1
danube:~ #
To show how the DM MPIO setup works, we documented the following two test
scenarios:
Important: The setup uses DM MPIO with the iSCSI software initiator
linux-iscsi-4.0.188.18 and the IP failover mechanism of the DS300. We tested
it successfully at the time this book was written to show the possibilities of DM
MPIO. If you rely on a fully supported configuration, do not use this setup as it
is not supported by IBM! Also note that failover processing and options may be
enhanced in future releases of DS300 firmware (see 3.3.5, “DS300 failover”
on page 41). So the shown DM MPIO setup might not work with other failover
mechanisms than IP failover.