On Tue, 20 Mar 2018 00:55:01 +0000 Jörg Saßmannshausen wrote:
I am wondering if that is not what you would expect.
The long SMART test is quite thorough so the disc will be subject to
quite a
bit of stress. Thus, it could well be that the controller is slowing
down the
rest of the RAID as there is a bottle neck.
Long SMART tests are run on active RAID systems here all the time, this
is the only machine so far where this massive slow down has been noted.
The others might slow down a few percent, but a drop in the read rate
from ~400Mb/s to 30Mb/s is just horrible. I'm wondering if the disks on
this one system (the only machine here with this model disk) disable
readahead or command queuing or something of that sort when a long SMART
test runs. However, no change in the read ahead value is visible with
"blockdev --report" with and without that SMART test running. The disks
are 2Tb 6.0Gb/s SAS with 128Mb cache and 4.16ms latency.
Regards,
David Mathog
mat...@caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech
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