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.
27         drive you wish to unstripe.  This must be 0 indexed.
33 An example of undoing an existing dm-stripe
34 -------------------------------------------
47   SEQ_END=$((${NUM}-1))
55   for i in $(seq 0 ${SEQ_END}); do
56     dd if=/dev/zero of=member-${i} bs=${MEMBER_SIZE} count=1 oflag=direct
57     losetup /dev/loop${i} member-${i}
58     DM_PARMS+=" /dev/loop${i} 0"
62   for i in $(seq 0 ${SEQ_END}); do
63     echo "0 1 unstriped ${NUM} ${CHUNK} ${i} /dev/mapper/raid0 0" | dmsetup create set-${i}
66   for i in $(seq 0 ${SEQ_END}); do
67     dd if=/dev/urandom of=/dev/mapper/set-${i} bs=${BS} count=${COUNT} oflag=direct
68     diff /dev/mapper/set-${i} member-${i}
71   for i in $(seq 0 ${SEQ_END}); do
72     dmsetup remove set-${i}
77   for i in $(seq 0 ${SEQ_END}); do
78     losetup -d /dev/loop${i}
79     rm -f member-${i}
83 ---------------
86 Each core of the drive has segregated access to its LBA range.
94   ----------    ----------
98 aggregate drive without this unstriping, reads on one partition
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'