[Bug 1522925] [NEW] lvm snapshot write performance issue

[pdi]

Public bug reported:

Strange write performance issue after upgrading from ubuntu server x64
14.04 to 15.10.

Hdd's write speed is near 90-100Mb/s:
# dd if=/dev/zero bs=1M count=100000 of=/dev/sdb
Result: 102 MB/s

Checking write speed for simple LV:
# lvcreate -L 100g vghost -n lv1 
# dd if=/dev/zero bs=1M count=100000 of=/dev/vghost/lv1
Result: 32.5 MB/s

And for LV + snapshot:
# lvcreate -L 100g -s vghost/lv1 -n snap1
# dd if=/dev/zero bs=1M count=100000 of=/dev/vghost/snap1
Result: 19.7 MB/s

Any ideas how to fix that?

** Affects: lvm2 (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1522925

Title:
  lvm snapshot write performance issue

Status in lvm2 package in Ubuntu:
  New

Bug description:
  Strange write performance issue after upgrading from ubuntu server x64
  14.04 to 15.10.

  Hdd's write speed is near 90-100Mb/s:
  # dd if=/dev/zero bs=1M count=100000 of=/dev/sdb
  Result: 102 MB/s

  Checking write speed for simple LV:
  # lvcreate -L 100g vghost -n lv1 
  # dd if=/dev/zero bs=1M count=100000 of=/dev/vghost/lv1
  Result: 32.5 MB/s

  And for LV + snapshot:
  # lvcreate -L 100g -s vghost/lv1 -n snap1
  # dd if=/dev/zero bs=1M count=100000 of=/dev/vghost/snap1
  Result: 19.7 MB/s

  Any ideas how to fix that?

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