Re[2]: Web Server & Documents

Subject: Re[2]: Web Server & Documents
From: "Walker, Arlen P" <Arlen -dot- P -dot- Walker -at- JCI -dot- COM>
Date: Tue, 8 Apr 1997 15:52:26 -0500

Arlen P Walker
04/08/97 03:52 PM




Not to impugn Sue's wonderful explanation, but the techie in me screamed a
minor terminology correction:

When you store a file on a hard disk, the File Allocation Table
or other disk indexing scheme tracks the contents of individual
sectors. Even if store a single byte of information, that byte
will consume an entire hard disk sector. Disk indexing schemes
do not get any more granular than that -- it would take them
too long to retrieve information if they did.

The typical PC hard disk is formatted into sectors of 1K each.
(You can tell because that's the smallest file you'll find.)
You store the help file, it flows into contiguous sectors and
consumes about 32K of disk space. Even if you put it on a network
drive that's been "optimized for large files" -- that is, formatted
with sectors of 2K or even 5K each -- say 5K -- then the help
file takes up 35K of disk space. The difference is insignificant.

But, since *each file* consumes a single sector of the hard disk, no
matter what its size, those 300 individual HTML documents
consume 300K of disk space -- one document in each sector. If
your hard disk is formatted with 5K sectors, all of a sudden
that HTML doc set consumes 1500K disk space -- and it's the
exact same content as the 32K help file.

The dependency isn't "sector size;" the dependency is "minimum allocation
unit." On some systems this is the sector. Those systems allow for variable
sector sizes. Other systems maintain a fixed sector size, but allocate in
"clusters" ("extents" is another term used) consisting of a variable number
of sectors.

In DOS, a typical sector size is 512 bytes, while the cluster (minimum
allocation unit) is 2 sectors. In early days, when DOS was limited to a
32MB disc size, some drive vendors got around this by changing the sector
size.

Other operating systems have kept the same sector size but varied the
number of sectors in an allocation unit. For example, the Macintosh OS has
a constant sector size of 512 bytes, but the allocation block size varies
with the size of disc. The largest I've seen is 53 sectors. Which means a
single-character file, stored on that disc, would use 26.5K all by itself.


Have fun,
Arlen
Chief Managing Director In Charge, Department of Redundancy Department
DNRC 224

Arlen -dot- P -dot- Walker -at- JCI -dot- Com
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