My reason for speed is writing, in particular. I want to be able to dump as many jpgs as I can onto the drive without losing frame rate. Not just on personal installs, but on customer installs. Anything to improve performance is always welcome.
In my personal setup, I am running the following:
Pentium D dual-core (model 915, I think), 2.8 GHz overclocked (currently, I've been messing with speed ratios) to 3.2 GHz, 3 Gig RAM (DDR2-800, I think), 3 x 146 Gig U320 15k-RPM SCSI drives on a PERC3 RAID controller running hardware RAID-5. I realize a drawback of write speed with RAID-5 over RAID-0, but I want the drive redundancy in my installs so I try to go with something along these lines for any higher-end setup. Any system I install is running Fedora Core (8, in this case).
ext3 seems to do "OK" for writes, but if multiple cameras are writing at 15-20fps, there are some drops. CPU load never
goes over 1.5 (2.0 on a dual-core is like running 1.0 on a single-core/CPU machine, working well but not over-working). Writing keeps up "for the most part", but as I mentioned, it gets some dropped frames occasionally. This system has 5 cameras all running 640x480 (analog bttv) with 3-4 zone modetect on each camera. When cameras are idle, it runs at .1-.2 load....when running full rate on multiple cameras at once, with a montage up, it pegs 1.5 on the load. The system runs as server only, run-level 3, with everything disabled except what it needs to run the web server and ZM. It also serves as my primary web server for outside ZM. I run extended ring buffers...so there are LOTS of jpegs being dumped to the drive every interval...and I LOVE using gobs of shared memory.
I've been reading a bit recently about the hack for libjpeg apparently giving more speed on jpeg writes. Is there truth to this?
Also, anyone do any tweaking on hardware-based RAID cards? I'm using cached writes, trying to utilize the cache on the PERC controller. I could likely bump up the RAM in the PERC, if that might help a bit, as well. Or play with other coptions (copyback, I assume, would slow it down tremendously).