something about lvm strip
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LVM Strip
How to Creat a Striped LVM
# lvcreate --type striped --stripes 2 --stripesize 256 vg1 -n lv_export -l 1526178 /dev/sda /dev/sdb
$ cat /etc/lvm/backup/vg1
# Generated by LVM2 version 2.02.168(2) (2016-11-30): Thu Feb 27 07:38:24 2020
contents = "Text Format Volume Group"
version = 1
description = "Created *after* executing 'lvcreate --type striped --stripes 2 --stripesize 128 vg1 -n lv_export -l 1526178 /dev/sda /dev/sdb'"
creation_host = "host1.example.com" # Linux host1.exampletv.com 4.9.0-11-amd64 #1 SMP Debian 4.9.189-3+deb9u2 (2019-11-11) x86_64
creation_time = 1582807104 # Thu Feb 27 07:38:24 2020
vg1 {
id = "7ISf3c-EyNh-H1I7-GUJU-xA9b-m519-leUFLf"
seqno = 2
format = "lvm2" # informational
status = ["RESIZEABLE", "READ", "WRITE"]
flags = []
extent_size = 8192 # 4 Megabytes
max_lv = 0
max_pv = 0
metadata_copies = 0
physical_volumes {
pv0 {
id = "QX8y4x-EQPO-PVUR-yvoG-Qg9l-PxZq-PZWQ4f"
device = "/dev/sda" # Hint only
status = ["ALLOCATABLE"]
flags = []
dev_size = 6251233968 # 2.91096 Terabytes
pe_start = 2048
pe_count = 763089 # 2.91095 Terabytes
}
pv1 {
id = "4W1wAI-fLHP-8HFj-4EJp-WZ8m-006q-IWIdDn"
device = "/dev/sdb" # Hint only
status = ["ALLOCATABLE"]
flags = []
dev_size = 6251233968 # 2.91096 Terabytes
pe_start = 2048
pe_count = 763089 # 2.91095 Terabytes
}
}
logical_volumes {
lv_export {
id = "yPjmOp-MOx3-ZkA2-Sn7l-IKmI-ItMN-D5VR7P"
status = ["READ", "WRITE", "VISIBLE"]
flags = []
creation_time = 1582807104 # 2020-02-27 07:38:24 -0500
creation_host = "host1.example.com"
segment_count = 1
segment1 {
start_extent = 0
extent_count = 1526178 # 5.82191 Terabytes
type = "striped"
stripe_count = 2
stripe_size = 256 # 128 Kilobytes
stripes = [
"pv0", 0,
"pv1", 0
]
}
}
}
}
Try Sequential Write with dd and verify it with blktrace
# dd if=/dev/zero of=/export/test.img bs=16k count=1920000 oflag=direct
As blocksize is set to 16k in dd, 8 requests will be sent to 1 underneath device then switch to another one since stripe size in lvm was set to 128k.
259,2 13 57 0.000514041 3272 A WS 89662304 + 32 <- (254,0) 179320416
259,2 13 64 0.000545028 3272 A WS 89662336 + 32 <- (254,0) 179320448
259,2 13 71 0.000575317 3272 A WS 89662368 + 32 <- (254,0) 179320480
259,2 13 78 0.000606383 3272 A WS 89662400 + 32 <- (254,0) 179320512
259,2 13 85 0.000637837 3272 A WS 89662432 + 32 <- (254,0) 179320544
259,0 13 57 0.000668819 3272 A WS 89662208 + 32 <- (254,0) 179320576
259,0 13 64 0.000700293 3272 A WS 89662240 + 32 <- (254,0) 179320608
259,0 13 71 0.000731709 3272 A WS 89662272 + 32 <- (254,0) 179320640
259,0 13 78 0.000763453 3272 A WS 89662304 + 32 <- (254,0) 179320672
259,0 13 85 0.000794049 3272 A WS 89662336 + 32 <- (254,0) 179320704
259,0 13 92 0.000824249 3272 A WS 89662368 + 32 <- (254,0) 179320736
259,0 13 99 0.000855601 3272 A WS 89662400 + 32 <- (254,0) 179320768
259,0 13 106 0.000886607 3272 A WS 89662432 + 32 <- (254,0) 179320800
259,2 13 92 0.000917480 3272 A WS 89662464 + 32 <- (254,0) 179320832
259,2 13 99 0.000948469 3272 A WS 89662496 + 32 <- (254,0) 179320864
259,2 13 106 0.000980183 3272 A WS 89662528 + 32 <- (254,0) 179320896
259,2 13 113 0.001017346 3272 A WS 89662560 + 32 <- (254,0) 179320928
259,2 13 120 0.001049972 3272 A WS 89662592 + 32 <- (254,0) 179320960
259,2 13 127 0.001081212 3272 A WS 89662624 + 32 <- (254,0) 179320992
259,2 13 134 0.001112461 3272 A WS 89662656 + 32 <- (254,0) 179321024
259,2 13 141 0.001143800 3272 A WS 89662688 + 32 <- (254,0) 179321056
259,0 13 113 0.001175234 3272 A WS 89662464 + 32 <- (254,0) 179321088
259,0 13 120 0.001206920 3272 A WS 89662496 + 32 <- (254,0) 179321120
259,0 13 127 0.001237859 3272 A WS 89662528 + 32 <- (254,0) 179321152
259,0 13 134 0.001268335 3272 A WS 89662560 + 32 <- (254,0) 179321184
259,0 13 141 0.001299716 3272 A WS 89662592 + 32 <- (254,0) 179321216
259,0 13 148 0.001330172 3272 A WS 89662624 + 32 <- (254,0) 179321248
259,0 13 155 0.001361460 3272 A WS 89662656 + 32 <- (254,0) 179321280
259,0 13 162 0.001391684 3272 A WS 89662688 + 32 <- (254,0) 179321312
259,2 13 148 0.001423254 3272 A WS 89662720 + 32 <- (254,0) 179321344
259,2 13 155 0.001455034 3272 A WS 89662752 + 32 <- (254,0) 179321376
259,2 13 162 0.001486733 3272 A WS 89662784 + 32 <- (254,0) 179321408
259,2 13 169 0.001517787 3272 A WS 89662816 + 32 <- (254,0) 179321440