How to track down abysmal performance ata - raid1 - crypto - vg/lv- xfs

From: Dominik Brodowski
Date: Wed Aug 04 2010 - 03:37:07 EST


on a production system I run kernel 2.6.35 and

XFS (rw,relatime,nobarrier)

on a

lvdevice of a vgroup

consisting of five

dm-crypt devices (cryptsetup -c aes-lrw-benbi -s 384 create)

, each of which runs on a

md-raid1 device (mdadm --create --level=raid1 --raid-devices=2)

on two

750 GB ATA devices.

The read performance is abysmal. The ata devices can be ruled out, as hdparm
resulted in acceptable performance:
> Timing cached reads: 9444 MB in 2.00 seconds = 4733.59 MB/sec
> Timing buffered disk reads: 298 MB in 3.02 seconds = 98.73 MB/sec

How can I best track down the cause of the performance problem,
a) without rebooting too often, and
b) without breaking up the setup specified above (production system)?

Any ideas? perf(1)? iostat(1)?

Thanks & best,

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