[TriLUG] rhel 3.0 es swap partition over 2.0 gb

[Marty Ferguson]

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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