We have a system whose RAID array has performance problems. We see I/O
maxing out at throughputs far below the spec of the controller and even
well below that of individual discs attached to it.
The RAID controller from Areca is configured with 2-off RAID volumes and
has 4-off 6TB discs attached to it. I would like to be able to access the
4 discs individually, e.g. to be able to dd them to /dev/null to check on
their performances. I know we could JBOD the discs and do S/W RAID but
this is a production system and in any case the point of having a H/W RAID
controller is to avoid this!
This shows the configuration,
# lsscsi -gs
[0:0:0:0] disk Areca ARC-1226-VOL#000 R001 /dev/sda /dev/sg0 199GB
[0:0:0:1] disk Areca ARC-1226-VOL#001 R001 /dev/sdb /dev/sg1 11.8TB
[0:0:16:0] process Areca RAID controller R001 - /dev/sg2 -
I know that some access to the individual discs attached is possible
because the smartmontools utility smartctl can do it, e.g.,
# smartctl -i -d areca,1 /dev/sg2
smartctl 7.0 2018-12-30 r4883 [x86_64-linux-3.10.0-1160.80.1.el7.x86_64] (local build)
Copyright (C) 2002-18, Bruce Allen, Christian Franke,
www.smartmontools.org
=== START OF INFORMATION SECTION ===
Model Family: Western Digital Red
Device Model: WDC WD60EFRX-68L0BN1
etc...
I was hoping to use 'sg_dd if=<???> of=/dev/null' or similar. I could not
find what I was looking for at https://sg.danny.cz/sg/ or elsewhere. Is
this possible? Can anyone give me some pointers?
Many thanks
Tom Crane
--
Tom Crane, Digital Electronics Engineer, Dept. Physics, Royal Holloway, University of London, Egham Hill,
Egham, Surrey, TW20 0EX, England.
Email: T.Crane@xxxxxxxxxx
