SUMMARY: Sun-3/xx maximum disk size ?

From: Carsten B. Knudsen (
Date: Thu Jul 22 1999 - 05:40:20 CDT

I got 10 replies ranging from "Not likely" to a concise explanation why this
is indeed so. Several posters reminded me that I forgot to mention the OS
version; it's SunOS 4.0.3, and for a number of reasons, upgrading is not an
option. For the record, the last SunOS version that runs on Sun-3 hardware
is 4.1.1_U1, which we have but don't use. Kevin and John hit the nail on
the head: The old SCSI driver can only issue the short SCSI READ, WRITE and
SEEK commands and therefore cannot reach beyond 2^21 blocks ~= 1 GB. Thanks
a lot. Oh, and special thanks to Michael for letting me know that I'm not
alone :-)

Thanks all,


  Carsten B. Knudsen Email:
  TERMA Elektronik A/S Phone: +45 8743 6000
  Hovmarken 4-6 Fax: +45 8743 6001
  DK-8520 Lystrup, Denmark (@home:

---------- Original posting ----------
Date: Wed, 21 Jul 1999 20:15:43 +0200 (MET DST)
Subject: Sun-3/xx maximum disk size ?

Greetings all,

  I know this is sort of an archaeologist question, but anyway, here goes:
We are trying to equip a Sun 3/80 with an external disk (don't ask) and we
are having problems to get it working properly. The disk is an IBM 4.5 GB
narrow SCSI-2, and first, I believed that is was enough to stay clear of the
2GB limit per _filesystem_. Now, it looks mostly like we have to write off
everything above 1 (one!) GB, in which case it appears to behave reasonably
well. Can this be true? Throwing away the space above 2GB was apparently
not enough; after mkfs'ing the last filesystem (from 1 to 2 GB), the root
FS was gone AWOL...
  Any hints to this one will be appreciated, and I will of course summarize
what I hear or find out - for whomever might be interested :-)

best regards,


---------- Replies:
From: Darren Dunham <>

Can't think of any reason that would be true. I don't have any
experience with the hardware that you're using, SunOS 4 shouldn't have
any such limit

Darren Dunham                

---------- From: Wade Stuart <>

You may want to know that the 3/80's are on suns not supported / not tested lists for y2k certification.


---------- From: Michael Baumann <>

Hey there... someone else with the dinosaur technology running :) In our case, it is 3/260s, we have 3 still in service. Here is the bad news: 1.05 GB is the largest media we could support. My guess is the same for you. We've been getting used drives to replace the original ESDI 480 drives that have died over the years (yes we replace the ESDI with SCSI, but thought you'd like to know )

-- Michael Baumann Optivus Technology Inc.

---------- From: Roger Fujii <>

uh, what OS did you end up running on this? 4.1.4? (can't remember when 68K suns were EOLed). You might want to be sure whatever you are using is patched.


---------- From: Kevin Sheehan {Consulting Poster Child} <>

Yep - the problem here is the old disk driver. It only uses SCSI Group 0 commands (CDBs) which only have 21 bits of block address. 512 bytes is 2^9 bits, so 21+9 == 30. 2^30 is 1GB.

I don't have all my old notes around, but I *thought* that it was fixed before the demise of SunOS that supported sun3x machines.

l & h, kev

---------- From: Matthew Stier <>

Older bootproms had limitations of 1GB for the root filesystem. Newer bootproms had 2GB limits. The newest bootproms have MUCH larger limit.

You can use all the disk, you just have to limit the root partition to 1GB. You can then use the other partitions (up to 2GB is size) as mountable filesystems.

Note: I just remembered a minor problem with older system that required a patch for drives greater than 1GB. What OS version are you running?

---------- From: Tim Pointing <>

I believe that you're right with the 1GB limit. There was, I believe, a problem addressing sectors beyond that limit.

May depend on patches applied to the OS, though.

-- Tim Pointing

---------- From: "Tang, TY" <>

Hi Carsten, You didn't mention what Solaris OS you are using. Tried upgrading the OS first?

Best rgds, TY Tang

---------- From: John DiMarco <>

Yes, 1GB is the limit for disks on Sun3 machines. Those systems rely on SCSI group 0 commands, which can't address blocks beyond 2^21-1, i.e. 2097152 or greater; a block is 512 bytes, so you're out of luck past 1GB. Ten years ago, this was not a big deal, since at the time you would be hard-pressed to find a SCSI drive larger than 1GB.



---------- From: Casper Dik <>

Could be a problem, yes. (Originally, sun4c/sun4m) couldnt' handle those disks either in SunOS 4.1.1. but a patch was produced.

Not sure it was code shared with sun3 or whether it was ever fixed.


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