Re: Amiga RDB partition support for disks >= 2 TB

[jdow]

On 20180628 04:38, Martin Steigerwald wrote:
> Martin Steigerwald - 28.06.18, 13:30:
> > jdow - 28.06.18, 12:00:
> > > On 20180628 01:16, Martin Steigerwald wrote:
> > [â]
> >
> > > > > That brings to the fore an interesting question. Why bother with
> > > > > RDBs
> > > > > over 2TB unless you want a disk with one single partition? This
> > > > > Win10
> > > > > monster I am using has a modest BIOS driver partition for the OS
> > > > > and
> > > > > a giant data partition. That smaller partition would easily work
> > > > > with
> > > > > any RDB/Filesystem combination since 2.0. So there are some good
> > > > > workarounds that are probably "safer" and at least as flexible as
> > > > > RDBs, one Linux has used for a very long time, too.
> > > >
> > > > Well, my use case was simple:
> > > >
> > > > I had this 2 TB disk and I choose to share it as a backup disk for
> > > > Linux *and* AmigaOS 4.x on that Sam440ep I still have next to me
> > > > desk here.
> > >
> > > EEEEEEK! The hair on my neck is standing up straight! Have you heard
> > > of SAMBA? The linux mail server firewall etc machine has an extra
> > > 4TB
> > > disk on it as a backup for the other systems, although a piddly 4TB
> > > is small when I save the entire 3G RAID system I have. It's a proof
> > > of concept so.... A full backup on a 1gig Ethernet still takes a
> > > looooong time. But backing up even an 18GB disk on an Amiga via
> > > 100Base-t isn't too bad. And disk speeds of the era being what they
> > > were it's about all you can do anyway.
> >
> > Heh, the thing worked just fine in Amiga OS 4. I got away with it
> > without an issue, until I plugged the disk to my Linux laptop and
> > wrote data onto the Linux file system. Mind you, I think in that
> > partition marked LNX\0 I even created a Linux LVM with pvcreate. Do
> > you call that insane? Well it probably is. :)
> >
> > And as an Amiga user I could just return to you: I clicked it, it did
> > not warn, so all is good :)
> >
> > But yeah, as mentioned I researched the topic before. And I think
> > there
> > has not even been an overflow within the RDB:
> > > The raw, theoretical limit on the maximum device capacity is about
> > > 2^105 bytes:
> > >
> > > 32 bit rdb_Cylinders * 32 bit rdb_Heads * 32 bit rdb_Sectors * 512
> > > bytes/sector for the HD size in struct RigidDiskBlock
> >
> > http://wiki.amigaos.net/wiki/RDB_(Amiga_Rigid_Disk_Block)
> >
> > Confirmed by:
> >
> > The .ADF (Amiga Disk File) format FAQ:
> > http://lclevy.free.fr/adflib/adf_info.html#p6
> >
> > But what do I write, you know the RDB format :)
> >
> > So just do the calculation in 96 Bit and you all are set :)
>
> For sectors.
>
> Or
>
> 3*32+9 (for 512 bytes per sector) = 105 bits
>
> for bytes.
>
> > Now that is a reason for 128 Bit CPUs :).
> >
> > Muuhahaha.

And if you make the logical block size 65536 you need 128 bits or 10^something 
big = 2^128.
{^_-}