Degradation Functionality Asterisk

We have a FreePBX Distro. Centos install on VMWare 6. At more than 150 simultaneous calls are seeing a problem with Asterisk. Calls for a long time are processed, do not always have the sound, the audio channel is connected through 6-10 seconds, AMI brakes. Some сalls was dropped.

We have a call centre with call recording.

We have:
Asterisk - 13.5
FreePBX -
Network adapter - 1Gb/s
RAM - 8Gb
CPU - 16 CPU
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 46
model name : Intel® Xeon® CPU E7540 @ 2.00GHz
stepping : 6
cpu MHz : 1997.833
cache size : 18432 KB
physical id : 3
siblings : 4
core id : 3
cpu cores : 4
apicid : 15
initial apicid : 15
fpu : yes
fpu_exception : yes
cpuid level : 11
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts mmx fxsr sse sse2 ss ht syscall nx rdtscp lm constant_tsc arch_perfmon pebs bts xtopology tsc_reliable nonstop_tsc aperfmperf unfair_spinlock pni ssse3 cx16 sse4_1 sse4_2 popcnt hypervisor lahf_lm epb dts
bogomips : 3995.66
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:

150 simultaneous calls is a lot for a VM even if everything is g711.
Are you doing any transcoding? Recording all 150 simultaneous calls is probably not helping either.

Try increasing the RAM. As far as I know you need about 1gb for math, and 64mb for every concurrent call in previous versions of Asterisk. That means on a 8Gb server you could expect ~110 concurrent calls assuming there are no other limiting factors.

We don`t use transcoding. All calls goes with g711, but we use “canrenivite (directmedia) = no”.

We recording about 100 simultaneous calls.