David Lang wrote:
On Sat, 2 Apr 2005, Andreas Dilger wrote:
given that this would let you get the same storage with about 1200
fewer
drives (with corresponding savings in raid controllers, fiberchannel
controllers and rack frames) it would be interesting to know how
close it
would be (for a lot of people the savings, which probably are within
spitting distance of $1M could be work the decrease in performance)
For benchmarks like these, the issue isn't the storage capacity, but
rather the ability to have lots of heads seeking concurrently to
access the many database tables. At one large site I used to work at,
the database ran on hundreds of 1, 2, and 4GB disks long after they
could be replaced by many fewer, larger disks...
I can understand this to a point, but it seems to me that after you
get beyond some point you stop gaining from this (simply becouse you
run out of bandwidth to keep all the heads busy). I would have guessed
that this happened somewhere in the hundreds of drives rather then the
thousands, so going from 1500x73G to 400x300G (even if this drops you
from 15Krpm to 10Krpm) would still saturate the interface bandwidth
before the drives
But in this case probably not - Ken increases IO capacity until the CPUs
become saturated.
So there probably isn't a very large margin for error, you might need
2000 of the slower
SATA disks to achieve a similar IOPS capacity.
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