Local channel and disc util

I noticed that when i using the local channel, and I use disk some process near 100 percent, begin to lose RTP packets in the voice. when used SIP channel this is not observed.
I understand that local chanel used hard disk, if so then which path it use disk , and it is possible to mount this path in the memory?

A Local channel does not use a hard disk directly, it may be if you are recording or playing back a file. As well if you have extreme I/O problems it can cause problems for everything regardless if things are doing I/O as the system can become starved of resources.

If you are using direct media with SIP, the audio could be bypassing Asterisk and therefore not affected by the fact that you are overloading the system.

Asterisk is a real time application with timing constraints of under 20ms. You should not be mixing it with other applications that heavily load the physical machine on which it is running.