Migration strategy?

David Collier-Brown davecb at canada.sun.com
Wed Oct 10 04:59:04 GMT 2001

Justin Chapman wrote:
| Well now, I'm setting up a Samba based server to replace an
| aging NT4 print server.  It's going to serve about 60 printers
| and be used by at least a few hundred people.  As you all know,
| when you are replacing a production server late one night, 
| knowing that the change could affect hundreds of users, you 
| kinda want everything to go smoothly.  :)   

	Let's assume that the same printers are being served by
	both the old and new machine, and the old machine is
	called "printers".

	Install the new Samba server as "new_printers", and
	put up one printer on it, with the same name as one
	on the NT machine (say, "lp").  Connect it to the NT
	printer via smbclient.  Set up one directly-connected
	printer (say, "lp2"), and make sure they both work.
	Do a quick measurement of the time it takes to print
	to the two printers
		- when it's quiet
		- during the busiest period of the day
	counting only the time it takes to get the print job
	to show up in queue.  This is to make sure you can
	slip the new machine in "in front' of the old without
	making things too slow.

	Now do the reverse: attach the Samba printer to the NT
	machine, and measure the speed of the fallback setup.

	The additional time should be small compared to the time it
	takes to get a print job through the queue. If it takes
	30 seconds and the queue is usually 2-3 minuets long,
	then you're safe.  If it takes 30 minutes and the queue
	takes 3, you've a problem!

	Once new_printers can print on all the existing printers
	via the NT machine, announce that you're moving department
	X's printers to the new machine. Don't move anything!
	After a few days, walk around department X, making sure that
	everyone knows they're to use new_printers. Then start
	moving the printers over physically, and do not make them
	available on NT.  If someone can't change over, recreate
	one printer connection on NT for them and go on to the
	next department.

	After about a month of short early-morning tasks you'll
	have all the printers moved over, and will have only
	a few recalcitrant customers left on NT.  Give them
	the NT machine to administer (;-))

	I'm joking: create a virtual server on the samba 
	machine called "printers", and shut down the NT. This should
	migrate any hard-coded server/printer pairs over to Samba.

	Alternately, you could do the rename early in the process,
	and have people who couldn't get to their printers use 	
	"old_printers", the new name of the NT.

	And so on: there's lots of usable variants of this scheme.

David Collier-Brown,           | Always do right. This will gratify 
Americas Customer Engineering, | some people and astonish the rest.
SunPS Integration Services.    |                      -- Mark Twain
(905) 415-2849                 | davecb at canada.sun.com

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