Upgrade from 32-bit to AMD-64?

[Mike Andrews]

Xin LI wrote:
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> Karl Denninger wrote:
> [...]
>> I guess I need to schedule the 2-3 hours of downtime..... the reason for
>> this, by the way, is that I have a dbms app on there that is getting too
>> RAM hungry for its own good (its a Quadcore CPU) and I'm up against the
>> RAM limit for 32-bit code.  The board will support more but 32-bit code
>> won't; ergo, the only way to get beyond this is to go to 64-bit.
> 
> Oh wait!  One thing you wanted to know is that, some database *can* have
> different on-disk format for 32-bit and 64-bit binaries.  Be sure to
> have a dump handy.  Last time I hit this on a MySQL "upgrade" between
> two servers, and I end up using its replication functionality.  The
> operation took longer time than I expected at the beginning.

For what it's worth, I did an in-place source upgrade on our MySQL 
server (for the same lack-of-memory reason) and didn't have any on-disk 
format problems.  In fact later on when troubleshooting data corruption 
problems that turned out to be bad hardware, I switched between 32-bit 
and 64-bit mysqld binaries without rebooting or dumping/reimporting the 
database.

BUT... there was no replication involved.  It wouldn't surprise me if 
the binlog or relay logs were in an architecture specific format. 
InnoDB and MyISAM tables don't appear to be.  This was over a year ago 
though, so test on a scratch box first and you may save yourself a bit 
of downtime.

The upgrade is a pain, and does have a lot of potential foot-shooting, 
and you have to immediately recompile ALL of your installed ports (and 
anything else not built from ports) to avoid mixing 32-bit and 64-bit 
shared libraries...  and that rebuilding ports time is where most of 
your downtime comes from if it's a production box.

If you're feeling lucky, the procedure's in the list archives somewhere 
and the super-short version is you turn your swap partition into a 
temporary amd64 root filesystem, installworld/kernel into that, boot 
into that, then mount and installworld/kernel on top of the old i386 
root filesystem from there, then boot into it and recompile all your 
ports (after reclaiming your swap partition for swap).  Or, the way I 
did it last time was to boot into a PXE diskless FreeBSD/amd64 install 
and use that to mount/install over the i386 stuff.

Definitely practice on a scratch system first. :)


-- 
Mike Andrews
Server Monkey
Fark, Inc
mandrews at fark.com