[afnog] Best Practices

[Phil Regnauld]

Geert Jan de Groot (GeertJan.deGroot) writes:
> 
> Ons line of thought these days - not sure if you should go this route,
> but it is at least something to consider - is that people create
> *dedicated*, (often virtual) machines for each of the services.
> The thought is that by installing only a single service on each host,
> maintenance and upgrading will be easier.

	If the OS you use has low overhead on upgrades (say, Debian-based
	distribution or sticking to FreeBSD releases).  But I did address
	this option in my post.  You can still consolidate multiple services
	on one physical box, but split them up using pseudo-virtualization
	such as jails or vserver.

	Xen is another solution, as the resource control is more fine-grained
	and the paravirtualization avoids the problems of traditional virtualization	(I/O in vmware/virtualbox for instance).

> as dictated by operational issues, by simply stopping the
> virtual machine, moving the image to another box, and re-starting it.

	Very big advantage indeed.

> Of course, if your application has high resource demands (such as
> mail virus scanning), then you don't virtualize, but make a physical
> box, perhaps more.

	Using pairs of RAID1 disks, and allocating each pair to one or two
	(max) jails in FreeBSD, you get the best performance, while confining
	access to the spindles (disks) to the machine that needs it.
	
	So if my machine has 6 disks:

	host:		jail1		jail2		jail3
	mountpoint:	/jail1		/jail2		/jail3
	type:		raid1		raid1		raid1
	disks		d0+d1		d2+d3		d4+d5

> (30 cabinets at least, all of them empty when I was there),
> for expansion and would meet higher volume demands by
> simply filling the next rack, and, over time, the rest of the racks.

	That's a good indicator of scalability.

	Phil