admin-guide/device-mapper/unstriped.rst

2 Device-mapper "unstriped" target
8 The device-mapper "unstriped" target provides a transparent mechanism to
9 unstripe a device-mapper "striped" target to access the underlying disks
10 without having to touch the true backing block-device.  It can also be
11 used to unstripe a hardware RAID-0 to access backing disks.
14 <number of stripes> <chunk size> <stripe #> <dev_path> <offset>
33 An example of undoing an existing dm-stripe
34 -------------------------------------------
47   SEQ_END=$((${NUM}-1))
56     dd if=/dev/zero of=member-${i} bs=${MEMBER_SIZE} count=1 oflag=direct
57     losetup /dev/loop${i} member-${i}
63     echo "0 1 unstriped ${NUM} ${CHUNK} ${i} /dev/mapper/raid0 0" | dmsetup create set-${i}
67     dd if=/dev/urandom of=/dev/mapper/set-${i} bs=${BS} count=${COUNT} oflag=direct
68     diff /dev/mapper/set-${i} member-${i}
72     dmsetup remove set-${i}
78     losetup -d /dev/loop${i}
79     rm -f member-${i}
83 ---------------
94   ----------    ----------
97 neighbor environments. When two partitions are created on the
99 can affect writes on another partition.  This is because the partitions
101 and make partitions on each new exposed device the two partitions are now
104 With the dm-unstriped target we're able to segregate an fio script that
106 when we run the test on a combined drive with partitions, we were able
114 ------------------------------------------------------
118   dmsetup create nvmset0 --table '0 512 unstriped 2 256 0 /dev/nvme0n1 0'
119   dmsetup create nvmset1 --table '0 512 unstriped 2 256 1 /dev/nvme0n1 0'
128 ---------------------------------------------------------------
132   dmsetup create raid_disk0 --table '0 512 unstriped 4 256 0 /dev/mapper/striped 0'
133   dmsetup create raid_disk1 --table '0 512 unstriped 4 256 1 /dev/mapper/striped 0'
134   dmsetup create raid_disk2 --table '0 512 unstriped 4 256 2 /dev/mapper/striped 0'
135   dmsetup create raid_disk3 --table '0 512 unstriped 4 256 3 /dev/mapper/striped 0'