Bug 754960 - MD RAID performance regression
Summary: MD RAID performance regression
Keywords:
Status: CLOSED INSUFFICIENT_DATA
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: kernel
Version: 6.1
Hardware: x86_64
OS: Linux
unspecified
medium
Target Milestone: rc
: ---
Assignee: Jes Sorensen
QA Contact: Red Hat Kernel QE team
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2011-11-18 11:50 UTC by Eugene Apollonsky
Modified: 2011-11-18 14:16 UTC (History)
2 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed: 2011-11-18 14:16:09 UTC
Target Upstream Version:

Attachments (Terms of Use)
Performance measurements (2.87 KB, text/plain)
2011-11-18 11:51 UTC, Eugene Apollonsky 		no flags Details
View All Add an attachment (proposed patch, testcase, etc.)

Description Eugene Apollonsky 2011-11-18 11:50:05 UTC 
Description of problem:
We have strange performance regression on RHEL6.1 versus RHEL5.2. See attachment for more details.

Actual results:
Average value and standard deviation of data rate on RHEL6.1 are worse than on RHEL5.2.

Version-Release number of selected component (if applicable):
Standard RHEL6.1 distribution.
Comment 1 Eugene Apollonsky 2011-11-18 11:51:36 UTC 
Created attachment 534377 [details]
Performance measurements
Comment 3 Jes Sorensen 2011-11-18 14:16:09 UTC 
Eugene,

dd from /dev/zero is really not a good way to test I/O performance, it is
impacted on how /dev/zero is generating data, it is single threaded etc.

Please try and benchmark it using a real disk benchmark tool like iozone,
or fio, etc.

In addition you do not provide any data about the memory of the system, number
of processors, how the disks are configured, etc.

Note that your RHEL5.2 benchmark numbers are very suspicious as well, the
fact that halt the numbers are exactly 2048 with no variation looks very
bizarre.

Best regards,
Jes
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