From: mks@cbmvax.commodore.com (Michael Sinz)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: 4 Gigs....and counting..
Keywords: SCSI Amigados
Date: 14 Aug 92 15:18:17 GMT
Reply-To: mks@cbmvax.commodore.com (Michael Sinz)
Organization: Commodore, West Chester, PA

rar@auc.UUCP (Rodney Ricks) writes:
>In article <1992Aug9.034453.4560@msuinfo.cl.msu.edu> jap@crs.cl.msu.edu (Joe Porkka) writes:
>>Due to the standard AmigaDOS device interface any particular
>>(logical) device is limited to 4gig. However, you may have many 4gig devices
>>attached. Theoretically you could have lets see...
>>In a A3000 which has 4 slots
>>	5 SCSI controllers, each can get at 7 unit of 8 drives each -
>>	giving you 5*7*8 or 280 drives. Say each drive was 4GIG.
>>	That leaves you with 1120 GIG of disk space.
>>	(You better have one *BIG* powersupply)
>
>First of all, is the 4 gig limit on the drives in this case, or the partitions?
>Aren't the partitions the logical devices?  If so, the amount of disk space
>is only limited by the number of devices that you can have (times the maximum
>partition size), and I think that is theoretically unlimited in the Amiga OS
>(if it is limited, I bet the limit occurs at the DOS level.).

The limit is that the device structures/names must fit in memory.
Other than this, there is no real limit.  After all, it is all linked lists.

>Actually, I think the number of logical devices is limited by the naming
>convention (three characters for the actual device name).

Device names can be up to 30 characters.  Mine show up as:  (from Info)

Mounted disks:
Unit      Size    Used    Free Full Errs   Status   Name
SOFTSYS:   32M   12875   52715  20%   0  Read/Write SoftSys
WB:        19M   30024   10224  75%   0  Read/Write WB
TYBALT:    11M   11326   11842  49%   0  Read/Write Tybalt
TEST:     681K    1272      91  93%   0  Read/Write Test
040:       40M   67514   14419  82%   0  Read/Write 040
JUNIOR:    29M   18462   41008  31%   0  Read/Write Junior
SOFT:    1401M 1682481 1188373  59%   0  Read/Write Main
RAM:        1K       1       0 101%   0  Read/Write Ram Disk
WB_2.x:    19M   18784   22160  46%   0  Read/Write System
DF0:      No disk present
DF1:      No disk present
T:         20M    2331   38667   6%   0  Read/Write T
Mail:      29M    9762   51654  16%   0  Read/Write Mail
Big:      499M   95434  928498   9%   0  Read/Write Big
BackUp:   583M  442553  753251  37%   0  Read/Write BackUp
Trash:    299M   50853  563489   8%   0  Read/Write Trash
Other:     99M   85835  118833  42%   0  Read/Write P
Work:     169M   28776  318142   8%   0  Read/Write Work

>Second, isn't the partition size limit under AmigaDOS 2gig?  I think I remember
>that it had a 2gig limit, and that signed arithmetic was used.

Well, we have not yet been able to test the system if it works with larger
than 2gig.  I do know that it will be a problem to have a file over 2gig due
to the fact that Seek() (and fseek()) take a signed value for the byte offset.

The size of the device (not partition) is limited to 4gig (32-bit) since
the Amiga .device I/O model takes byte offsets as a 32-bit number.  A device
driver could take a 8gig drive and make it look like two different units of
4gig each.

However, I claim that the number of people that will put a drive that is
over 2gig in size on their $500 Amiga coputer system will be rather low
for a while yet.  By the time this really becomes a problem, the fix will
have been done long ago.

/----------------------------------------------------------------------\
|      /// Michael Sinz  -  Senior Amiga Systems Engineer              |
|     ///                   Operating System Development Group         |
|    ///   BIX:  msinz      UUNET:  mks@cbmvax.commodore.com           |
|\\\///                                                                |
| \XX/                      HELP!  I am starting to like it here...    |
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Newsgroups: comp.sys.amiga.hardware