[HECnet] RT-11 filesystems, was Re: DECnet-RT?

[Thomas DeBellis]

32MB really was ginormous back in the day; our labs had RT on RK05's, 
which held about 2.5MB.  Way more than a DECtape.

That's a shame about the RT11 RP06 drive handler you wrote; that sounds 
like a fine piece of code.  Since the RP06 held something near 176 MB, 
how many partitions did you get?  5?  6?  What was the limit?

On 3/31/20 2:19 PM, Steve Davidson wrote:
> Dave,
>
> RT11's file system can only address 32MB of space.  It only uses a
> clustersize of "1" so it is limited.  Partitioning the disk into
> logical areas was the way the DU driver got around this.
>
> You are correct that the RM drives are limited to the first physical
> 32MB of disk space.  They did not use partitioning until the DU class
> of drives came out.  The reasoning was that the older drives would not
> be around much longer anyway so why bother.
>
> I wrote a driver (handler in RT11 speak) for the RP06 that eventually
> made use of the partitioning scheme that the DU devices used.  I got
> the idea from Greg Adams (the original author of the DU driver/handler)
> but alas, it is long long gone!  Oh well...
>
> -Steve
>
> On Tue, 2020-03-31 at 14:10 -0400, Dave McGuire wrote:
>> On 3/31/20 10:02 AM, Robert Armstrong wrote:
>>> RT11 has an architectural limit of 32Mb per file system.  Most disk
>>> drives, even way back then, are bigger than that and have to be
>>> partitioned if you want to use all the space.  This is an RT11
>>> thing,
>>> not a CDROM nor a PDP-11 nor a simh, feature.
>>    So, about that.  And please forgive the non-HECnet-related
>> question.
>>
>>    Like everyone here, I've run RT-11 since the dawn of time.  But
>> I've
>> never run it on a disk that's larger than 32MB that is also not MSCP.
>>
>>    On a (real) system at the museum the other day, I noticed that RT-
>> 11
>> has a driver for the RM02/RM03, a 67MB drive.  I went looking as I'm
>> bringing up a Fuji M2284K SMD drive, which (on an Emulex SC21 Unibus
>> controller) emulates two RM02s.  If RT-11 cannot partition an RM02
>> because it's not MSCP, then why does it have a driver for it?  Will
>> it
>> just use the first 32MB?
>>
>>    Or (similarly to Ethernet) was it just there to use "raw"?  I know
>> of
>> one installation (on an 11/70) that used RM02s for raw storage of
>> digitized audio, no filesystem.
>>
>>                -Dave
>>