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Subject3ware 9650SE-4PML RAID-1 Question: One reader process starves I/O to the rest of the system?
Hello,

I tried CFQ/deadline schedulers, when I run the following:

# /usr/bin/time dd if=/dev/sdb2 of=/raid6/sdb2.img

Behind which are 2 x Raptor 150GB disks, the system is pretty much unusable
when I control-c the dd, it comes back to life.

The RAID-6 is a 15-disk RAID-6 which does 600-700MB/s writes.

All cards are on PCI-e and have adequate bandwidth on a P55 board (DP55KG).

Are there any recommended tuning options for a RAID-1 configuration, such that
a heavy I/O read or write operation does not pause the system?

During the dd..

Drive Performance Monitor Configuration for /c1 ...
Performance Monitor: ON
Version: 1
Max commands for averaging: 100
Max latency commands to save: 10
Requested data: Instantaneous Drive Statistics

Queue Xfer Resp
Port Status Unit Depth IOPs Rate(MB/s) Time(ms)
------------------------------------------------------------------------
p0 OK u0 25 762 26.219 19
p1 OK u0 23 780 25.953 24
p2 OK u1 1 0 0.000 98
p3 NOT-PRESENT - - - - -

Justin.




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