Re: 8.0-RELEASE completed...

On Thu, Nov 26, 2009 at 09:57:58PM -0800, Gary Kline wrote:
> 
> 	Altho I am still some time from having my migration from the
> 	1998 Kayak -> 2009 Dell done and working, will it be possible
> 	to upgrade my 32bit 7.2-R, p4 to a 64bit 8.0? 

It is possible, but not easy. Upgrading from 7.x to 8.0 on the same
architecture is not that hard IMHO. Upgrading from i386 to amd64 on the same
release is doable but tricky; you need a spare root partition to install the
amd64 binaries. Combining these two sounds like a big can of worms to me. My
advice would be _not_ to do it.

It would be far easier to just install 8.0 on the new machine and migrate your
data and configuration files. You are going to have to build your ports from
scratch anyway, because you're switching to another architecture and another
major release.

As far as I know, the on-disk filesystem format hasn't changed. (unless your
old machine is still running UFS1. The default now is UFS2)

There are a couple of differences between 7.x and 8.0;
* The USB stack has been rewritten. I've had to change the following in
  /etc/devfs.rules: replace "add path 'usb*' mode 0660 group usb" with "add
  path 'usb/*' mode 0660 group usb" 
* The name of the tty devices has changed in /etc/ttys; ttydN -> ttyuN
  (impacts /etc/ttys)
* There have been a lot of changes in the kernel configuration. If you want a
  custom kernel, start anew from the 8.0 GENERIC kernel so you don't miss
  anything. 
* A lot of changes as well in /etc/src.conf (the file that defines which parts
  of the system are built from source)
* Network cards show up in dmesg and ifconfig, but not as devices in /dev (but
  that could be a configuration error on my part.)

All my configuration files are kept in a directory that is under revision
control by git(1), so I could show you exactly what changes I've made.

> 	would get that clear as a first step.  My Intell duo-core is
> 	very fast; would moving to the 64-bit system be a net gain or
> 	loss [in performance].  

There is no clear gain or loss answer to that one. It depends on the workload
you are running. On the plus size, amd64 has a lot more general registers
available in the CPU than i386. On the other hand, the binaries are
bigger. 

Since you're switching to another CPU, things like cache size will have a
major inpact. WRT single versus multi cores, my impression has been that the
individual cores in a multi-core intel CPU are somewhat slower that the core
of a similarly clocked single-core CPU. (based on some informal testing I've
done with povray). If your workloads are capable of running on multiple cores
(e.g. make jobs, different programs running concurrently) there will be a
significant speed increase.

You only _need_ amd64 if you are running out of address space on the i386
architecture. Having said that, I've been running amd64 on my desktop since
5.3-RELEASE more or less because I can, and it has worked fine ever since. Be
aware though that there are a few (most binary) ports that do not work on
amd64. You can see that in the port Makefiles by looking for things like
NOT_FOR_ARCHS and ONLY_FOR_ARCHS.

HTH,

Roland
-- 
R.F.Smith                                   http://www.xs4all.nl/~rsmith/
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