Subject: Re: Memory and Solaris 2.3

From: [email-masked] (Earl Barfield)
Date: 22 May 1994 00:31:15 -0400

>My SPARC Classic, running Solaris 2.3, currently has 16Mb RAM. It seems
>to spend a lot of its time paging, especially when receiving data by NFS from
>a PC-NFS-based PC, and also when gcc goes to work on a large set of sources.
>The ram is arranged as 4x4Mb, with 2 slots free, and it seems that I can
>only get 4Mb or 16Mb SIMMS, ie to upgrade to either 24Mb or 48Mb, without
>junking the existing SIMMS.  I have two questions

>1.  Is it worth upgrading to 24Mb?  Will I notice a large reduction in the
>    amount of paging (especially with PC-NFS)?

Sorry, I don't specific answers for your paging questions or your
questions about which Simms will go with which other Simms.  I just
thought I'd point out one HUGE pitfall that we jumped into (with bothe
feet) just 3 days ago.  If you add RAM, make good and damn sure that
your swap partition is still larger that your physical RAM.  We added
32MB to an LX, but didn't increase the size of the swap.  We had a few
unrelated problems and typed "sync" at the prom monitor and it
proceeded to dump 64MB (physical memory size) into out 32MB swap
partition... needless to say it wasn't pretty.  It wrote all over our
root partition and the machine wouldn't even boot.  We had to go get
the CD-ROM and re-install.  Those Simms should come with a da-glow red
sticker warning you of this. :-)
-- 
Earl Barfield  --  Operations Department / Information Technology  
Georgia Institute of Technology, Atlanta Georgia, 30332
Internet: [email-masked]    [email-masked]
          [email-masked]         [email-masked]

---

From: [email-masked] (Robert Montjoy)
Date: 26 May 1994 13:27:11 GMT

In article <[email-masked]>,
Thomas Paul Anderson <[email-masked]> wrote:
>Earl Barfield ([email-masked]) wrote:
>[...much deleted...]
>:   The guys from Sun assured me that a configuration with more physical
>: RAM than swap is perfectly okay.  I'm not really sure what happened
>: and it's impossible to go back now and piece it together.  It was much
>: more critical to get the machine back up and running than it was to
>: figure out exactly how things got messed up.  We added another disk drive
>: when we re-installed the OS, so all the old partition information is
>: lost and even vfstab has been changed.
>
>Still, I thought the rule of thumb was to allocate a swap space that is 
>twice the size of your physical ram?  Is that no longer true?

Under Solaris2.x Virtual memory space is "real" memory
plus swap....  However, under SunOS4.1.x you need at least as much
swap as real. If you have less swap than real additional memory
is only used for disk buffers and the like. The "rule of thumb"
of swap space equals twice the memory is generally overkill for
machines with lots of memory(greater than 48-Meg) but of course
it depends a lot on what your application mix is.

Actually under Solaris2.x you can run without swap space if you have
enough real memory. We did this for a while on a SPARCserver 1000
with 192-Meg of memory but it is hard to get crash dumps(and boy did we
need the crash dumps) without a swap partation.

-- 
Rob Montjoy  		     - Computer Engineer/Systems Administrator
University of Cincinnati     - Electrical and Computer Engineering 
E-Mail: [email-masked]   - Personal or Other E-Mail

--  To Save the Earth. The Humans must die.