From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from elasmtp-curtail.atl.sa.earthlink.net ([209.86.89.64]:55338 "EHLO elasmtp-curtail.atl.sa.earthlink.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932371AbeF1MbZ (ORCPT ); Thu, 28 Jun 2018 08:31:25 -0400 Subject: Re: Amiga RDB partition support for disks >= 2 TB To: Martin Steigerwald Cc: Michael Schmitz , Geert Uytterhoeven , Matthew Wilcox , David Sterba , Linux FS Devel , Linux Kernel Mailing List , Jens Axboe , linux-m68k References: <20180425154602.GA8546@bombadil.infradead.org> <4710936.m2SbBcP6dP@merkaba> <51008870.LIDn3ZZdjm@merkaba> From: jdow Message-ID: <6b25bd4b-d218-55a0-6687-b17fbf7e5c97@earthlink.net> Date: Thu, 28 Jun 2018 05:31:18 -0700 MIME-Version: 1.0 In-Reply-To: <51008870.LIDn3ZZdjm@merkaba> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: 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: >> […] >> >>>>> 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. {^_-}