Re: Big hard drives

["Michael L. Hitch" <mhitch%msu.oscs.montana.edu@localhost>]

Patryk =?iso-8859-2?Q?=A3ogiewa?= <silverdr%inet.com.pl@localhost> writes: 
> From: Bernd Sieker...
> 
> >> You have written "blocks". Thus if the blocksize (aka fs fragment size?) is
> >> e.g. 1024 bytes - then NetBSD can access 4*(1024^4) i.e. 4096GB. Right?
> 
> >No, the BSD ffs has blocks and frags, which are different. Typical block
> >size is 8k, frag size 512 bytes, but different values can be chosen
> >when 'newfs'ing.
> 
> >I hope I'm making sense.
> 
> Yes. You are. Thought the default "frag" was 1024 bytes for some time though.

  I belive the blocksize defaults to 8192 and the fragment size is 1/8 of that,
or 1024.  I'm fairly certain the fragment size can't be smaller than 1/8 the
block size, so using larger blocks sizes requires larger fragment sizes.

> Alright. I understand. Now as I know that it should work, I would like to ask
> the last question or rather come back to the one I started with: What are the
> _exact_ limits for the AmigaOS access?
> 
> I want to know the exact limits because I don't want to set-aside 200 or 300
> MB's of the drive's space just because I don't know where to set the border
> between AmigaOS accessible part of the drive and the NetBSD accessible one.
> 
> Knowing exactly the limits would allow me to do optimal partitioning and this
> is the point why I bother all of you with my questions.

  The 'exact' limit would be 4294967296 bytes (0x100000000) due to the 32-bit
byte offset used by the disk driver.  That would be 8388608 (0x08000000) disk
blocks.  That value would be the first "illegal" value, which is were the
disk driver starts wrapping around at block 0 and scribbling all over your RDB
blocks.  Anything at that location or greater would be in-accesible to AmigaDOS
without changes to the disk driver and any applications calling the disk driver.

Michael
---
Michael L. Hitch                        mhitch%montana.edu@localhost
Computer Consultant,  Information Technology Center
Montana State University, Bozeman, MT     USA