[CentOS-virt] which virtualization platform to choose

Wed Jul 28 10:00:46 UTC 2010
Luke S Crawford <lsc at prgmr.com>

Grant McWilliams <grantmasterflash at gmail.com> writes:

> What kind of situation would you be trying to run 160 DomUs per Dom0? I'd be
> curious about your particular
> needs for having that many DomUs per Dom0. Did you run into a hard coded
> limit on the number of DomUs you could have?

Well, the smallest server that it is economical to buy and run has 32GiB
ram.   (this /may/  change when the amd 4100 chips come out;  I haven't
started poking them yet.  The numbers certainly /look/ good.) I give 1GiB 
to the dom0 (a little liberal, yes, but it's cheap insurance, I say)  

My smallest plan is 64MiB ram.   Now, I don't sell many of those, because
for a dollar more a month, I'll give you 128MiB ram, which is /much/ more
useful.   (I mostly keep the 64MiB plan out of pricing consistency;  I 
charge a dollar a month for every 64MiB ram, and then $4/month for each 
account for support/abuse overhead.) 

so I fill up those 31GiB with 128MiB ram guests, that gives me
248 guests on one server.  Even if I didn't sell anything smaller than 
256, which is my most popular plan, that'd still be 124 guests, which 
is more than I've gotten with the stock kernel (with two block and one 
network device per guest;  one disk is a read-only 'rescue' image, 
accessable via pvgrub, and the other is the customer's disk.) 

Now, I put all guests 512MiB ram and smaller on one server, so it's 
very rare that I go over 150 guests per server outside of testing, but
as you can see, I want the option to do so.

If you are interested in the details of what I had to change:


Luke S. Crawford
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