text: Raid controller problem - Spiceworks
  by Real_WizardHawk on Oct 4, 2013 at 19:43 UTC
  I have put together a few servers in my day, but I have an odd issue on one that has me stumped and I can't think of a better place to find some expert feedback.
  We have a surveillance recording server that just dumps digital video to drives 24/7.
  It has an Adaptec 6805 8 channel Raid controller on it fully populated. It has two smaller drives in a Raid 1 for the OS/software and 6 JBOD 3Tb Seagate constellation enterprise grade SATA drives for the video.
  We also have 3 of those same drives on the MB sata ports.
  Everything works, however the 6 JBOD data drives on the controller are working WAY below rated IO capacity.
  Each camera is at a constant bit rate of 6Mbps. On the drives connected to the MB we can put 5-6 of them on it and everything is fine. In fact in the resource monitor (win 7 pro) it shows a drive use of somewhere between 4-10% on these.
  On the drives connected to the controller we see them at 99% use time and we drop frames.
  I tested to see where the bottleneck was and find that removing cameras from one whole drive does nothing to others so each channel is it's own bottleneck. I put just two cameras on one drive and it was showing around 48% drive use time in resource monitor. Again, way worse than the same drives on the MB controller. They shouldn't be half way maxed out with just 12Mbps of streaming data on them.
  This is running on an Asus P8B-X MB with a Xeon E3-1245v2 CPU. I have it installed in the first PCIe slot (blue) as this is using integrated graphics.
  Each drive is shown as 'optimal' in the Adaptec manager and I can find no place to change settings for any IO related functions.
  Am I missing something really easy here?
  Oct 4, 2013 at 23:11 UTC
  I assume the JBOD is configured on the adaptec and presented to the server OS as a single large volume. In this case, one physical drive could be the destination for ALL writes since the data is just spanning across. As the volume fills and transitions to a new physical disk, all new writes are going to that next disk.
  Are the MB connected drives also JBOD? On the adaptec, if a JBOD disk member fails, does it kill the array? I assume it does. That's a pretty fragile setup either way. You need to take advantage of those multiple drives and setup some sort of striping, hopefully with redundancy (like raid10, not raid 5 or 6.)
  Real_WizardHawk Oct 7, 2013 at 19:31 UTC
  They are not grouped together at all. Each drive is its own volume. We only used the adaptec card because this unit needed 12 hard drives. The only two that are in a Raid are the small ones for the OS/Software.
  I went up and removed 3 drives from that controller and put them on the MB and the remaining 3 JBOD on it that are recording data are all still maxed out with very little traffic going to them. I doubt striping would solve anything as all 3 are maxed out with the traffic they have already.
  I'm sort of stumped on what is causing the bottleneck. The Adaptec manager software reports that the drives are negotiated at 6Gb/s speed and all are listed as optimal with no errors or problems.
  Anyone know of a good free HD load testing app? Something that can push a drive and give feedback on the IO rate?