Path: utzoo!utgpu!water!watmath!clyde!rutgers!gatech!hubcap!ncrcae!ncr-sd!hp-sdd!hplabs!hp-pcd!hpcvca!charles
From: charles@hpcvca.HP (Charles Brown)
Newsgroups: comp.sys.amiga
Subject: Re: Semicoherent flame about Amigados.
Message-ID: <4410018@hpcvca.HP>
Date: 13 Feb 88 00:37:42 GMT
References: <644@nuchat.UUCP>
Organization: Hewlett-Packard Co., Corvallis, Oregon
Lines: 46

>>Please, after you finish the fast file system... get a reliable on.
>>It doesn't have to be big: 720K per diskette would be fine. But it
>>needs to have real sectors to act as firewalls when corruption
>>occurs (as it invariably does). 

>	Silly, they *are* real sectors... they simply do not have the
>*space* normally put between sectors.  The problem is with the way
>AmigaDOS and the trackdisk.device handle it.

Wasn't it posted here that the Amiga does not wait until the index
mark to write out the track?  That is the real reason the sectors do
not act as firewalls.  The physical location of any particular sector
on the track is random from one write to the next.  Thus an error in
one sector (or even in the gap) may appear in any other sector with
the next write.

Clearly, the cost of fixing this reliability problem is performance.
Each track write will take up to twice as long because of the disk
rotation latency.  Sigh...

>	One major improvment, and one reason why IBM-PC
>harddisks/floppies seem more reliable, is to put in lots of
>self-checking in the software... "do I *really* want to do this
>operation.. lets check this structure checksum here, that structure
>checksum over there ... ho hum, I guess it's ok, start the DMA". 

One thing I liked from some CP/M systems was being able to read a disk
knowing there were errors.
   SECTOR READ ERROR.  A=Abort, I=Ignore, R=Retry.
Most of the files I cared about were text.  Ignoring the error allowed
me to reconstruct most of the file.  I could then edit out the junk
introduced by the sector error.  Of course, this may not be ideal for
an unsophisticated user.  But in a less than perfect world we often
have to put up with less than perfect solutions.  After all, the
perfect solution is a disk which does not make errors.

>	Another reason PC disk drivers seem more reliable is the inherent
>single tasking nature of the PC.. it usually doesn't freeze in the middle of
>a disk operation.
>					-Matt

It also does not pause... and then write to the disk just when you
were about to reboot.  I have trained myself to wait 5 seconds after
the LED goes out before I reboot.  The Amiga is the only computer I
have needed this for.
	charles@hp-pcd