Hint for older Xserve/ Pro Tower users - faster disks
  • I found that with a large number of high-motion cameras, my older systems were starting to fall behind on disk I/O. The CPU works great (I have 8 cores for cheap in the older machines) and I have lots of headroom there, but when I have 9 cameras with simultaneous motion pushing to disk at 4MP and 12fps, things were starting to get lossy. The problem is when all the cameras detect motion at the same time; they don't always go at once, but when they do, I got frame loss.

    USB wasn't cutting it for SSD-attached drives because of slow wire speeds on the older system. So the only other option was something on the PCI bus.

    I purchased one of the OWS Accelsior drive cards (https://eshop.macsales.com/item/OWC/SSDACL6G.S/) and then a cheapo used high-performance 128G Intel SSD to put on it. Works like a charm - I get 83 MB/s onto the drive (664 mbps) according to FileWritingTest which is plenty to keep up. Due to the small size of the drive, I just copy off files with rsync every few minutes onto a spinning drive. It seems the serial streaming via rsync is able to keep up. Then I just use crontab to delete old files off the big spinning drive array with something like this to delete files older than 7 days (it runs every 2 hours):

    find /Volumes/Videostorage1/* -mtime +7 -exec rm -r \{\} \;

    JT
  • Sounds like a great setup, thanks for sharing! I haven't come across this card before, it's very interesting - useful and inexpensive. I'm a little surprised that your write speeds aren't faster than 83 MB/s, although this could be a function of the older PCI bus or the particular SSD you are using.
  • Apparently I forgot what SSD I put in this machine - it's a SanDisk SSD Plus 120GB, and not the Intel I bought which I guess went into another system. Not sure if anything faster on the SSD side would make much of a difference, though.

    The spinning 1TB Hitachi SAS drives on the internal Xserve bus get 38MB/sec, so the SSD is still twice as fast. I suspect it's just that this is an 11 year old machine, so it's not super-speedy on the backplane.

    (and those that argue that this is a waste, old machines, blah blah blah etc. etc. - the machines are "free" and the electricity is free, as it is an oversized solar array running everything, so a few bucks for SSD upgrades is a no-brainer.)

    JT
  • Yes, I think this is an excellent use of older hardware, thanks for sharing your experiences!

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