On 11/01/2011 07:08 AM, Sanjana Shari wrote: > But if I use the other part of the disk to map. The command is not successful > > [root@bladelinux01 root]# dmsetup create half1 --table "102401 102399 linear /dev/loop0 102400" > device-mapper: reload ioctl failed: Invalid argument > Command failed You have to always map the whole table (starting at sector 0). If you see syslog, you can see why device-mapper: table: 254:2: linear: Gap in table device-mapper: ioctl: error adding target to table Anyway, for the info how it works, example how to switch active table: 1. create linear device mapped to /dev/sdb # dmsetup create x --table "0 10000 linear /dev/sdb 0" # dmsetup table x 0 10000 linear 8:16 0 2. Remap the first half of device to another target, here "error" - load new (yet inactive) table # echo -e "0 5000 error\n5000 10000 linear /dev/sdb 5000" | dmsetup load x - so now you have one active table and one inactive (prepared for switch) # dmsetup table x 0 10000 linear 8:16 0 # dmsetup table x --inactive 0 5000 error 5000 10000 linear 8:16 5000 3. switch to new (inactive) table (note that "dmsetup suspend" here is implicit) # dmsetup resume x # dmsetup table x 0 5000 error 5000 10000 linear 8:16 5000 If you want more info about this low level DM operation, read http://people.redhat.com/agk/talks/FOSDEM_2005/ http://mbroz.fedorapeople.org/talks/DeviceMapperBasics/ (old, but still useful, I hope :-) Milan -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
