[TriLUG] rhel 3.0 es swap partition over 2.0 gb

Kevin Flanagan kevin at flanagannc.net
Thu Apr 1 23:03:41 EST 2004


On Thu, 2004-04-01 at 21:35, Marty Ferguson wrote:

I think that there's something else here, perhaps it is the 32 bit arch,
I seem to recall that as a limit with other Operating Systems, older
than Windows too....  ;')  I want to say that 2GB limit was in VMS going
a long ways back, but am not sure.  Perhaps google, or the wayback
machine will help.  Off I go, digging through the archives.



Kevin

> When Linus rewrote swapping for the {I think it was) 2.2 kernel release,
> I imagine that he figured 2G was plenty.  Also, the limit is _per_ swap
> partition,
> which is limited to like 8 or 16 (I think I believe I recall I suppose)
> I've never used more than 3 swap partitions simultaneously, all declared in
> /etc/fstab.
> So, assuming the limit on the number of partitions is 8, that still allows
> for a total of 16G of swap space.
> 
> The increase to 2G was a big deal at the time, and there were
> significant improvements other than just the increased size limit.
> You are correct - It is indeed a 32bit address space limitation.
> 
> I'm sure you can google and get lots of interesting historic information
> using the site: search option for Linux World and such.
> This was all happening circa back in the day when Jim Ray was into Whorled
> Peas.
> 
> Marty
> 
> -----Original Message-----
> From: trilug-bounces at trilug.org [mailto:trilug-bounces at trilug.org]On
> Behalf Of J Hays
> Sent: Thursday, April 01, 2004 8:54 PM
> To: Triangle Linux Users Group discussion list
> Subject: Re: [TriLUG] rhel 3.0 es swap partition over 2.0 gb
> 
> 
> Marvin Blackburn wrote:
> 
> > What are the consequences of a swap partition over 2.0 gb.
> > I know that Redhat says it each partion should be < 2.0.
> > Is this just wasted space, or can problems occur.
> >
> > ------------------
> > Marvin Blackburn
> > Systems Administrator
> > Glen Raven
> > "He's no failure.  He's not dead yet" --William Lloyd George
> 
> I'd be interested in any information on this as well. That 2 GB
> swap space ceiling rings a bell.
> 
> A few years ago I worked for a Sun reseller and our most senior
> Sun engineer repeatedly warned customers and junior admins (like
> me) that creating a single swap partition over 2 GB (in Solaris)
> was asking for trouble. I seem to recall some actual problems
> manifesting on a customer's high-end Sun system (I think it was a
> Sun E6500, with 8 or 10 GB of memory) under heavy load. The
> problems were cured by changing the single, large swap partition
> into a 2 GB swap partition plus a swap file. The customer
> resisted implementing the proposed solution because there was
> little documentation of this limit on docs.sun.com, but we
> finally found something - not an explanation of why - just a
> published warning against exceeding 2 GB on the swap partition.
> 
> It makes me wonder if there could be some intrinsic problem with
>   2GB as the size of the swap file (something to do with 32-bit
> addressable space?) or perhaps Linux engineers merely copied the
> limitations in the UNIX code, or something else ...
> 
> Jonathan
> 
> 
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