||Oracle Tips by Burleson
Disk I/O Tuning
Chapter 1: Disk Capacity - The Two-Edged Sword
achieve the same IO capacity as we had with our 112-9 gigabyte disks
we would need to buy 2.7 (952/348) times the needed capacity of 180
gigabyte drives even with their superior access times and MB/s
transfer rates. The values in table 1-1 reflect the performance
values when that drive capacity was the maximum available. Of course
as we saw in Figure 1.7, if we replace the old 9 gig drives with the
new 40 gig (36 gig formatted) drives with the sustained transfer
rate of 58 MB/s we get 28*58 or a total transfer rate of 1624 MB/s
which would require 28 of either the new 73 or 180 gig drives in
order to match the IO rate from the 28-40 gig drives.
we used the new 40 gig drives, we could expect better IO transfer
rates of up to 70 percent based on IO rate, while if we bought the
180 gig drives based on storage capacity alone we would see a
decrease in IO capacity of over 270%. This is why IO capacity should
be the driving factor in disk drive purchase, not storage volume per
The above text is
an excerpt from:
Oracle Disk I/O Tuning
Disk IO Performance & Optimization for Oracle
by Mike Ault
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