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From: bennett@mp.cs.niu.edu (Scott Bennett)
Newsgroups: comp.sys.next
Subject: Re: SCSI formatter
Keywords: scsi formatter fujitsu M2263S
Message-ID: <1991Feb17.042905.31075@mp.cs.niu.edu>
Date: 17 Feb 91 04:29:05 GMT
References: <15616@celit.fps.com> <5214@media-lab.MEDIA.MIT.EDU> <15652@celit.fps.com>
Organization: Northern Illinois University
Lines: 40

In article <15652@celit.fps.com> rory@fps.com (Rory Bolt) writes:
>Well, I had hoped I would not get flamed too badly for posting a binary and I
>was wrong to do it. Sorry. I need a volunteer with FTP access to upload a new
>version of my utility, but first a few responses to the many questions/comments
>I have recieved:
>
>1) [text deleted --SJB]
>
>2) It is my understanding that the NeXT filesystem has a minimum allocation
>length of 1024 bytes, regardless if your sector size is 512 bytes or 1024 bytes.
>Thus there should be no disadvantages to 1024 byte sectors.

     If the file system is indeed the 4.3BSD FFS as advertised, then the
minimum *block* allocation (the important number for performance) is
4096 bytes.  The minimum fragment size, which is relatively unimportant
w.r.t. performance, is 512 bytes.  Several UNIXes that claim to use the
FFS have a minimum fragment size of 1024 bytes.  Fragments are suballocated
from *whole* blocks and any given file will have at most less than one
block's worth of fragments.  The important consideration for performance,
then, is how many sector reads/writes must be done to read/write a block.
Space efficiency is, of course, a separate issue, but in a system that
uses a fixed logical block size for a whole device (e.g. a UNIX disk
partition) will usually benefit from using a larger physical block (sector)
size because less space is wasted in interblock gaps.
>
>3) [more text deleted --SJB]
>						Rory
>						rory@fps.com


                                  Scott Bennett, Comm. ASMELG, CFIAG
                                  Systems Programming
                                  Northern Illinois University
                                  DeKalb, Illinois 60115
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