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 \{\} \;

  • 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.)

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

Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!