A Small Production System - Disk Performance

Uncompressed (or lightly compressed) video needs lots of disk space. More than that, if you’re capturing live video, that disk capacity needs to be fast.

I’m using a Blackmagic Intensity Pro video capture card. It will capture 1080p uncompressed if your system can support that. It comes with a handy Disk Speed Test that measures read/write performance and translates that into frames per second of video at different formats.

In the original build of my video production box described in my previous post, I configured the two Hitachi Deskstar E7K1000 HDE721010SLA330 1TB drives as a hardware RAID 0 array with a 128K strip size connected to the onboard Intel ICH10R controller. Here’s what Blackmagic’s Disk Speed Test gave me:

This is a stark contrast to running with older drives in the same configuration. Write speeds enabling 122fps for 8-bit 4:2:2 720p video should be more than enough for good captures. Running the DiskMark test that is part of PassMark Software’s PerformanceTest 7.0 indicated a sequential read rate of 222MB/s and a sequential write rate of 186MB/s.

For grins, I added another two 1TB drives to create a 4-way RAID 0 array with a whopping 3726GB capacity. The two new drives were a pair of Seagate Barracuda 7200.12 ST31000528AS, which have the same 32MB buffer as the Hitachi Deskstars. Running Speed Test again gave me:

So in this configuration, it looks like I might be within spitting distance of being able to do 8-bit 4:2:2 1080p captures (even though the disk write frame rate measured 72fps, Blackmagic recommend a healthy margin and also SATA drives get slower the fuller they are). DiskMark indicated a sequential read rate of 341MB/s and a sequential write rate of 304MB/s.

I suspect that the only way I’m going to improve on this performance is to use a hardware RAID card with an on-board processor and dedicated memory.

Here’s the summary then:

	2-way RAID 0	4-way RAID 0
8-bit YUV 4:2:2 1080p	54fps	72fps
8-bit YUV 4:2:2 720p	122fps	163fps
Sequential Read	222MB/s	341MB/s
Sequential Write	186MB/s	304MB/s

Comments

• Anonymous
  February 20, 2010
  You say of the Blackmagic Intesity Pro that "It will capture 1080p uncompressed if your system can support that."  Are you sure you are getting 1080p with Intensity Pro?  The literature for the product does not say that it will support 1080p, and I've not managed to get it to (not that I spent much time trying, I must admit).  If you're really capturing 1080p on an Intensity Pro, I'd love to know how you're doing it.  Thanks.

• Anonymous
  February 20, 2010
  I captured 1080p24 out of my MacBook Pro a couple of days ago. Though I was capturing via Cineform's HD capture utility so it was compressing to Cineform on the fly, which is my preferred way of working at this time. I have to say that having spent more time with the Intensity Pro, it seems to be incredibly finicky about what it will and won't take in terms of video. Of course, dealing with computer output is notoriously hard and there are so many variables.