use disk cache, not use shared memory, or use minimum shared memory -- 1M only. not sure if it's possible to completely disable shared memory in latest eAccelerator. per my past experience with eAccelerator, 1M is the minimum shared memory size and you have to set it.
no need set up an additional ram disk like following:
tmpfs /lsgzip tmpfs rw,uid=99,gid=32016,size=8G,nr_inodes=10k,mode=077 0 0 0
just use /dev/shm, it's ram disk already created from you by linux.
if you have 256G memory, your /dev/shm may be allocated 128G. check it by:
create a sub folder under /dev/shm, say /dev/shm/eaccelarator, set eAccelerator's disk cache location to it. so eAccelerator actually store opcache in memory.