[mdlug] Moving to Debian 64bit - Lessons Learned?

[Michael S. Mikowski]

On Friday 31 July 2009 04:02:42 am Stan Green wrote:
> I am going to attempt to move my main desktop PC to Debian 5.0.2 64bit.
> (I'm doing it on a different PC, so I can keep my current one running until
> I have the new one running correctly.)  This is my first attempt at a 64bit
> Linux install. Are there any lessons others have learned from making this
> switch or with Debian 64bit? Has anyone had success/failure with VMWare
> Workstation 5.5 in this configuration?
>
> FYI: My main reason to go to 64bit is to be able to access more than 3gb of
> memory. Running VMWare can quickly chew up memory.
>

My advice is don't do it.  Really, all the headaches you get from 64 bit are 
not made up with speed or memory except in instances that usually occur only 
in very high-volume database or number crunching situations.

First, speed:  http://www.phoronix.com/ has shown repeatedly that 64 bit 
desktops rarely run faster for most desktop tasks.  In fact, for most apps, 64 
bit often runs slower.

Second, memory: You can install a 32 bit kernel with large memory support.  
Last year we installed 2 Dell 1950's with 8 64 bit cores and 16G ram each to 
handle ~ 3 billion MySQL inserts and ~750 million reads per day.  We intended 
to move it to a 64 bit OS to access all that memory.

However, we discovered using the 32 bit PAE kernel provided by RedHat (RHEL 5) 
handled the memory just fine.  A check of free or top showed all 16G available.   
Exactly how that memory was accessed (e.g. if it were "paged" or not) I never 
investigated since MySQL ran like a top.

<http://www.cyberciti.biz/tips/redhat-enterprise-linux-4gb-plus-ram-
support.html#comments>

So unless you are doing some serious crunching, 64 bit is probably simply not 
compelling.  Avoiding all the hassle of 32 bit library and driver 
incompatibilities probably is :)


Cheers, Mike

ps Last I checked (8 months ago) VMWare only supported 32 bit kernels for the 
host OS.  So unless that has changed, there is little benefit there either.