[smartmontools-support] Long SMART test trashes RAID read rate.
David Mathog
mathog at caltech.edu
Tue Mar 20 00:59:28 CET 2018
Hi all,
I spent today trying to figure out why one of our big PowerEdge systems
suddenly could not read from a RAID at more than 30Mb/s. Oddly while
that was the rate for one process,it would also do two at that speed.
The test was just:
dd if=bigfile bs=8192 of=/dev/null
Go up to four processes and it topped out at around 80Mb/s. The normal
read rate is on the order of 400Mb/s.
After much futzing around it turned out when a long SMART test is
running on any disk on the system (A) which has this problem the IO goes
down to 30Mb/s. It doesn't matter which disk is running the test. It
doesn't get worse if they all are. The system we have which is most
like the first system (C) does not have this issue.
A C
Centos 6.7 6.9
RAM 512 512 Gb
CPUs 56 40 (actually threads)
PowerEdge T630 T630
Xeon E5-2695 E5-2650 (both v3)
speed 2.30GHz 2.30Ghz
cpufreq? yes no
PERC H730 H730P
SAS disk ST2000NM0023
SAS disk ST4000NM0005
There are a bunch of small differences between the two systems so it is
hard to say for sure which is the actual culprit. I have never seen
this issue before on another system.
Anybody else seen this? Is it the disks, the controller, the
combination of the two??? Cpufreq thrown in for good measure?
Thanks,
David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech
More information about the Smartmontools-support
mailing list