[dm-devel] device mapper multipath and /sys/block/XXX/device/queue_dept

[Janec, Jozef]

Hello All,

I just tried change the  queue_dept for one lun which is connected to the server with device-mapper multipath

LUN1 (360060e80047f280000007f28000010b2) dm-146 HP,OPEN-V
[size=25G][features=1 queue_if_no_path][hwhandler=0]
\_ round-robin 0 [prio=12][active]
 \_ 2:0:5:85  sdbky 71:1760  [active][ready]
 \_ 2:0:4:85  sdbfg 134:1440 [active][ready]
 \_ 1:0:2:85  sdaoc 66:1216  [active][ready]
 \_ 0:0:5:85  sdaob 66:1200  [active][ready]
 \_ 3:0:2:85  sdalz 135:848  [active][ready]
 \_ 3:0:1:85  sdxv  128:592  [active][ready]
 \_ 1:0:1:85  sdvd  67:752   [active][ready]
 \_ 0:0:4:85  sdul  66:720   [active][ready]
 \_ 3:0:0:85  sdfp  130:176  [active][ready]
 \_ 2:0:3:85  sdbu  68:128   [active][ready]
 \_ 0:0:3:85  sdbs  68:96    [active][ready]
 \_ 1:0:0:85  sdbl  67:240   [active][ready]

I set on all devices /sys/block/xxx/device/queue_depth to 4

But after few sec...

They were changed to 5, and the number is increasing until it reach 16. Is there something in device mapper multipath what is changing the queue_depth?

Thanks

Jozef