High Load, IOWait, and SSD offloading?

[noloco]

Hi,

I have a zoneminder box that is pretty new, running quad core AMD, SSD drive for the OS drive, and a 2 x 4TB RAID0. I am getting fairly high load ~6.0 - 8.0, running 9 HD cameras. It looks like I have a lot of IOWAIT when I am doing system stats. I'm wondering if there is a good way to have Zoneminder cache to the SSD drive and then offload to the RAID? It could be I just have it setup wrong. All zoneminder files go to the raid directly currently. Is there a better way to set this up?

Thanks.

[TheKorn]

It looks like I have a lot of IOWAIT when I am doing system stats. I'm wondering if there is a good way to have Zoneminder cache to the SSD drive and then offload to the RAID?

The only thing I'm aware of that will use an SSD as a write cache for HD arrays is if you use a ZFS file system. If you don't have a whole lot of stuff already on your array there are tons of great reasons to use ZFS aside from this, so you might want to check into it before you get too far.

How much RAM are you running? Linux is usually pretty good about caching things into RAM if it's otherwise unused. If you're on the low side might want to spring for more. (ZFS loves RAM, so even if you go that route it won't be wasted.)

[iconnor]

HD camera make for a lot of data... hopefully this will be helped by the video storage code which might be in 1.28. Storing individual jpgs the way we do makes for a ton of small writes.

I wonder if you can tune the IO subsystem to heavily cache writes. Might help. FS's that do well with tons of small files might be good. HD jpgs are probably kinda bigger though. Can you tell us how big on average the jpegs in your events dir are?

Also, how many fps are you trying to achieve?

[Fatman]

Hi,

You could try enabling bcache in the linux kernel to an SSD, see http://en.wikipedia.org/wiki/Bcache

[hesral]

I have an 8 core amd with 6 1TB in a raid10 array. I have 75 cameras working. Lots of low fps analogue cameras, but some high resolution ip cameras as well. I saw some very high load during the busy hours. I reduced logging and turned off statistics. I haven't had problems with load since then. If I need to tweak zones, I turn on stats again, but only at night.