How many concurrent calls an Asterisk server can support?

I have a Amazon large EC2 instance running centos 6.5 and Asterisk many concurrent calls this server may support?
I am sure people are running Asterisk on virtual servers. Hope, some one can give some data. Thanks.

There is just no way of telling this without testings. Do some call simulations and benchmark the server if you need a good answer.

Besides of hardware, Asterisk by default can serve 10 concurrent calls, or if CPU load average is less than 0.9 or if the amount of free memory is more than 1 megabyte. So, you may play with these settings in asterisk.conf. (Please correct me if I’m mistaken)

;maxcalls = 10			; Maximum amount of calls allowed.
;maxload = 0.9			; Asterisk stops accepting new calls if the
				                ; load average exceed this limit.
;maxfiles = 1000		        ; Maximum amount of openfiles.
;minmemfree = 1			; In MBs, Asterisk stops accepting new calls if
				                ; the amount of free memory falls below this
				                ; watermark.

Many people also think that not each type of virtualization is good for Asterisk, for example OpenVZ.

The default is to apply no limit to the number of calls. The commented out values given in the sample configuration are not always the defaults.

The same applies to maxload.

I agree with dejanst, I prefer to test with SIPp or some other tool that I feel comfortable to use.