How to put movie file to disk cache?

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http://serverfault.com – I have a streaming project with ~ 500 video streaming connections at the same time. I built a server follow as: CPU E3-1230 RAM 16GB HDD: SATA II 4x2TB with Raid 10 && SSD 2x120GB Intel 520 with Raid 0 Currently, I installed Lighttpd with mod_h264 and mod_flv to streaming and mod_secdownload to anti hotlink. But I have problem about IO performance, I want to put HOT movie file to disk cache (two SSD Disks with Raid 0) and lighttpd will be read hot movie file from SSD improve streaming speed. I don't know do that, please give me a solution ? Thanks so much :) (HowTos)