/var/lib/varnish tmpfs recommended size and multiple _.vsm files

[Web Teknik]

Hi,

After reading Varnish Book and Varnish wiki, we decided to put
/var/lib/varnish directory to tmpfs with following line in /etc/fstab

tmpfs                   /var/lib/varnish        tmpfs
defaults,noatime,size=128M        0 0


However, while trying restarting varnish, another shmlog file which is
named _.vsm.4311 is also stored under /var/lib/varnish/<host> whose
size is 42MB. As a result Varnish refused to start since disk is full.
We couldn't reproduce the issue that _.vsm.somenumber (PID?) is
created. Under which conditions multiple _.vsm files are created and
in order to prevent failure, what is the recommended size for
/var/lib/varnish directory?

Thanks in advance.