RE: BINARIES - San or Local Storage
- From: "Mark W. Farnham" <mwf@xxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 27 Aug 2004 13:42:48 -0400
Exactly, Mladen.
And of course since form factor sizes are somewhat standardized, instead of
using the higher density to make disks with smaller diameters and therefore
with proportionally shorter average seek times, they keep the diameter
constant and the size of the disk goes up but seek time only rises at high
expense of tiny relative improvments in engineering the mechanics of head
positioning. Sure, the lap time goes down as the RPMs go up, but you've
still got to move in and out radially to get to the right cylinder.
As the costs of SSD trend downward and writing to on board persistent memory
in duplicate using on board power on system power failure becomes standard,
we'll get to use more of the technology that overcomes the mechanical limits
in a scalable way.
mwf
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Gogala, Mladen
Sent: Friday, August 27, 2004 11:39 AM
To: 'oracle-l@xxxxxxxxxxxxx'
Subject: RE: BINARIES - San or Local Storage
Let me guess: drives have cache, and controllers have cache as well??
Seek time is defined as an average time that heads need to move from one
sector to another. Is a purely mechanical quantity, and I'm not aware of any
significant technology advances in moving heads from one place to another.
It's pure mechanics, which is essentially the same as it was 10 years ago.
What you're measuring is impacted by cache. It's the same thing as bicycle:
the look is much more modern, it contains carbon fibers, titanium and
modern materials, but I still have to pedal it uphill. Lance Armstrong
would probably beat me on a 20 years old bicycle without a problem. It's
the same with disk drives: not much new technology there. Density is
increased, disks are rotating faster, but the seek time is still the same.
--
Mladen Gogala
A & E TV Network
Ext. 1216
> -----Original Message-----
> From: Jesse, Rich [mailto:Rich.Jesse@xxxxxxxxxxxxxxxxx]
> Sent: Friday, August 27, 2004 10:32 AM
> To: oracle-l@xxxxxxxxxxxxx
> Subject: RE: BINARIES - San or Local Storage
>
>
> That's a pretty sad state then. Even my old 7200RPM 4.3GB FW
> SCSIs that = work threw out are 8.5ms. 15K spin SCSI
> Ultra320s should have an = average seek of about 3.5-4.0 ms
> Seagate Cheetahs are 3.6, for example.
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