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From: dillon@CORY.BERKELEY.EDU (Matt Dillon)
Newsgroups: comp.sys.amiga
Subject: Re: Amiga NFS
Message-ID: <8710182253.AA05929@cory.Berkeley.EDU>
Date: Sun, 18-Oct-87 18:53:36 EDT
Article-I.D.: cory.8710182253.AA05929
Posted: Sun Oct 18 18:53:36 1987
Date-Received: Mon, 19-Oct-87 03:05:14 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
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:	My understanding of the hard disk throughput problem is OS related, not
:driver related. From what I have heard, even DMA hard disks suffer greatly from
:this problem. NFS being a DOS device, would only share in this headache. The
:bottome line is, NFS can't run faster than a hard disk, bandwidth asside.
:Am I wrong?

	We are all familar with the ram disk (RAM:), and the floppy 
drive (DF0:).  The difference between the two is that the floppy goes 
through two levels of devices: DOS, and the trackdisk, and RAM: goes 
through only one level (no trackdisk).  RAM: accomplishes this by handling
all the DOS packets (openning files, traversing directories, etc....).

	Is DOS notoriously slow when dealing with the trackdisk.device?
The theoretical maximum throughput through a trackdisk.device can be 
characterized by VD0: or VDK: . The statistics are wildly different, going
from 119K/sec for VD0:, to 873K/sec for VDK: reading.

	The throughput of RAM: is about 873K/sec reading, so this can be
considered the 'theoretical' limit.  

	Thus, the slowness one experiences with HARD DRIVES is probably due
to an inefficient layout on the HD.  DOS has a bad habit of putting it's
sector lists far away from the data sectors themselves, causing lots of 
seeking when reading (two seeks every 32K ... yuccc!!!).

	An NFS to a host which uses a good layout can be *much* faster!
E.G. and NFS to a SUN or VAX host.

					-Matt