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Home -> Community -> Mailing Lists -> Oracle-L -> RE: BINARIES - San or Local Storage
http://www.storagereview.com/guide2000/ref/hdd/perf/perf/spec/posSeek.html
"The seek time of a hard disk measures the amount of time required for the read/write heads to move between tracks over the surfaces of the platters."
Mladen,
Ok, I'll agree that "seek time" does not include rotational factors. "Access time" is what I was throwing around. Mistakenly so.
http://www.storagereview.com/guide2000/ref/hdd/perf/perf/spec/posAccess.html
Access Time = Command Overhead Time + Seek Time + Settle Time + Latency
I did not mention that the blocks fetched by read ahead is highly significant and was nonzero and what really matters for an OLTP system would be the single block read time.
I also did not mention, that in my examples, the
drives used are "short stroked" and that at most only
50% is used for live datafiles, controlfiles, redo log
files.
this is a well known method of reducing the seek time,
which it then follows, reduces the (average) access
time. As the drives were 18 GB, 9 GB was kept as hot
which coincidentally I believe that Jonathan Lewis
cited as about as large an amount of data that one
would want on a single hard drive.
The other half is used for storing backup sets or is left unused. dark. so unavailable that windows Computer Management, disk management doesn't ask you if you want to format it, like it does for my ext3 partitions on the dual boot laptop. :)
my storage utilization ratios are not good.
guess I'll never get my picture in ComputerWorld Magazine with bad lighting where I look like I'm trying to figure out what to have for lunch.
Pd
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