I'm just after conformation (or not!) of something I've done for a long
time which I think is right - it certainly seem right, but one of those
things I've always wondered about ...
When creating an array I allocate drives from alternative controllers with
the thought that the OS/system/hardware might be able to better overlap
accesses to the devices - but it sort of assumes that the kernel drivers
(and/or mdadm) don't re-order accesses to the devices internally (I'm not
counting SCSI logical re-ordering here)
So. eg. an example I'm working on now - I have a server with 2 external
facing SCSI interfaces, and a box with 14 drives on 2 chains - so 7 drives
on each interface (I'd prefer less, but it's what I've got - it's a Dell
external box) sd{a-g} are on scsi0, and sd{h-n} are on scsi1, so I issue
the create command with:
mdadm --create /dev/md1 -n14 -l6 \
/dev/sda /dev/sdh \
/dev/sdb /dev/sdi \
etc.
I guess benchmarking it would be the way to really test it, but I'm not
after performance for this particular box - just after some thoughts as to
whether this is the "best" (or not!) way to do things, or if I'm wasting
my time doing it this way!
Thanks,
Gordon
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