[Bug 997695] [NEW] severe performance issue using mdadm raid5 on top of LUKS

[Bianco Veigel]

Public bug reported:

I've upgraded to 12.04 a few days ago and since this, the performance of
my crypto-drive is limited by CPU.

I'm running an MDADM RAID5 on top of 7 independendtly encrypted drives
(Seagate Barracuda XT 7200.12 2TB each encrypted using crypsetup /
LUKS).

The problem seems to be, that in 12.04 all encryption is done using only
a single CPU core. In 10.04 each crypt-device used its own thread
(kcrypt), that was the reason to encrypt each device independently and
build a raid on top of the crypto devices.

I'll attach a screenshot of munins iostat and CPU graph to illustrate
the difference before and after the upgrade

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

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: Incomplete

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https://bugs.launchpad.net/bugs/997695

Title:
  severe performance issue using mdadm raid5 on top of LUKS

Status in “cryptsetup” package in Ubuntu:
  New
Status in “linux” package in Ubuntu:
  Incomplete

Bug description:
  I've upgraded to 12.04 a few days ago and since this, the performance
  of my crypto-drive is limited by CPU.

  I'm running an MDADM RAID5 on top of 7 independendtly encrypted drives
  (Seagate Barracuda XT 7200.12 2TB each encrypted using crypsetup /
  LUKS).

  The problem seems to be, that in 12.04 all encryption is done using
  only a single CPU core. In 10.04 each crypt-device used its own thread
  (kcrypt), that was the reason to encrypt each device independently and
  build a raid on top of the crypto devices.

  I'll attach a screenshot of munins iostat and CPU graph to illustrate
  the difference before and after the upgrade

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