Path: utzoo!attcan!uunet!portal!atari!apratt
From: apratt@atari.UUCP (Allan Pratt)
Newsgroups: comp.sys.atari.st
Subject: Re: Disk Speedup
Message-ID: <1727@atari.UUCP>
Date: 13 Oct 89 17:44:24 GMT
References: <1407@ultb.UUCP> <1725@atari.UUCP> <819@lzaz.ATT.COM>
Distribution: comp.sys.atari.st
Organization: Atari Corp., Sunnyvale CA
Lines: 33

hcj@lzaz.ATT.COM (HC Johnson) writes:
>In article <1725@atari.UUCP>, jansen@atari.UUCP (Mark O. Jansen) writes:
>> >  Is there a program that will speed up disk access on my hard disk? I
>> >  ...Does TOS 1.4 help with this ? What can I do in the meantime?  
>> Yes, Rainbow TOS (a.k.a. TOS 1.4) helps with this.  A LOT.  ...

>... After 16-20 meg of copying, it gets noticeably SLOW!

It may be slow, but good lord, not as slow as TOS 1.2!

The "slow" part is the first write to a new file.  GEMDOS looks for the
first free cluster in the FAT, always starting from the beginning. When
there are 16 solid MB of allocated clusters, that's a lot of FAT
sectors to check before finding a free cluster.  On TOS 1.2, this is
REALLY APPALLINGLY SLOW!  On TOS 1.4, this is kind of slow. On TOS 1.4
with enough GEMDOS disk buffers to keep the whole FAT in RAM, it is
REALLY FAST!  Try Dfree on a 32MB partition in under 1 sec!

(Allocating the second, third, ... n'th cluster is not slow, because
there the search begins with the previous cluster, not the start of the
FAT.)

Ken Bad should have posted "CACHEXXX.PRG" here - if he hasn't, I'm 
sure he will.  If you use it and be sure XXX is equal to the sum of the
FAT sizes (in sectors) of your disks, GEMDOS will load them  up once
and never have to hit the disk for reading a FAT again!

It is not the case that the FAT is written after each allocation. It's
written when a buffer is re-used or the file is closed.

============================================
Opinions expressed above do not necessarily	-- Allan Pratt, Atari Corp.
reflect those of Atari Corp. or anyone else.	  ...ames!atari!apratt