Re: sector size of 2068?

Brandon S. Allbery KF8NH (allbery@kf8nh.apk.net)
Thu, 27 Aug 1998 21:51:02 -0300


In message <Pine.LNX.3.95.980827132719.204B-100000@chaos.analogic.com>,
"Richar
d B. Johnson" writes:
+-----
| On Mon, 24 Aug 1998, Peter wrote:
| > What would need to be changed to make a SCSI disk with sector_size
| > reporting back as 2068 work?
|
| In the SCSI controller BIOS setup, low-level format the drive using
| your new controller. The drive was apparently low-level formatted on
+--->8

We've been through that already. His question is, why can't we use it with
2068? (The reason he asked being that more space is "wasted" with 512-byte
sectors due to sector mark overhead.)

The short answer is that most of the kernel assumes that disk sector sizes
are a power of 2 and therefore can be represented via bit shifting 2068
isn't a power of 2, so isn't eligible. 2048 might well be doable, though,
if you really wanted it....

| optimization to select the proper head, etc. Therefore I doubt
| that the "real" block-size is 2068. In practice, it's usually
| 512 or a multiple thereof.
+--->8

It has been suggested that they chose a format that makes the disk look as
big as possible. That it's not *usable* in that format (to my knowledge, no
other OS does 2068-byte sectors either) isn't significant to marketroids
pushed to "demonstrate" their numbers....

-- 
brandon s. allbery	[os/2][linux][solaris][japh]	 allbery@kf8nh.apk.net
system administrator	     [WAY too many hats]	   allbery@ece.cmu.edu
electrical and computer engineering					 KF8NH
carnegie mellon university

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