RAID 5 for video capture

Smooth · 12 Oct 2007 at 18:47

I'm looking to build a system for capturing HD footage. For uncompressed 1280x720 footage at 30fps it requires a steady 80mb/s.

RAID 5 with 4 drives has been suggested to me, I personally would have thought that RAID 0 would provide faster write speed.

I was just wondering what controllers and drives people would recommend.

Carrying on from this thread: http://forums.overclockers.co.uk/showthread.php?t=17788393

rpstewart · 12 Oct 2007 at 20:57

I'd be going with a two disk RAID0 array as the capture target and a second array (RAID0, RAID5 or even a single disk) as the target for the h264 output. A 2 disk array of 7200.11s or AAKSs will give you sufficient write speed with plenty of headroom for the captures and by having a second set of disks your conversion process isn't going to be disk limited.

I wouldn't have thought that there was a need for redundancy on the capture target since the footage can be recaptured (or can it?), on the conversion target you could go for a redundant array if you want but it might be easier / cheaper to just have a decent backup strategy.

jhmaeng · 12 Oct 2007 at 23:15

RAID5 write performance is pretty dire unless you have some very expensive controllers with hardware processing.

Even if you wanted redundancy, RAID 01 or 10 might be a better option given that it doesn't involve any parity calculations so any motherboard RAID controller can offer the full speed.

m_cozzy · 13 Oct 2007 at 00:26

As above, raid 10 if you need speed and redundancy, raid 0 if you just need speed.

Smooth · 13 Oct 2007 at 00:51

rpstewart said:
A 2 disk array of 7200.11s or AAKSs will give you sufficient write speed with plenty of headroom for the captures and by having a second set of disks your conversion process isn't going to be disk limited.

That's what I was thinking of to begin with so I reckon I'll go with that.

Mr Jack · 13 Oct 2007 at 11:22

jhmaeng said:
RAID5 write performance is pretty dire unless you have some very expensive controllers with hardware processing.

This isn't true any more. Intel's IHC9R (found on most P35 mobos) is quite capable of producing high write speeds. It will up your processor usage, but if you're running Quad core that really doesn't matter.

Mr Jack · 13 Oct 2007 at 11:25

Smooth said:
I was just wondering what controllers and drives people would recommend.

I run a RAID 5 setup myself. But I've got to say, I'd recommend a RAID 0 setup for what you're describing unless you absolutely need redundancy.

rpstewart · 13 Oct 2007 at 11:42

Mr Jack said:
This isn't true any more. Intel's IHC9R (found on most P35 mobos) is quite capable of producing high write speeds. It will up your processor usage, but if you're running Quad core that really doesn't matter.

There was an interesting post on StorageReview a while back, it may actually be Vista that's indirectly providing better write speeds from onboard RAID5 solutions. It's all to do with Vista placing the start of a partition in a different place to XP and how that interacts with the stripe size of the RAID array. On XP you're guaranteed to have to do a load of extra parity processing because of the mismatch between the partition start and the stripe, with Vista if you get the stripe size right the number of calculations is vastly reduced.

Smooth · 15 Oct 2007 at 08:47

Mr Jack said:
This isn't true any more. Intel's IHC9R (found on most P35 mobos) is quite capable of producing high write speeds. It will up your processor usage, but if you're running Quad core that really doesn't matter.

So if I had a decent mobo with IHC9R I could achieve atleast a minimum of 80mb/s in RAID5?

I'm thinking of grabbing 4 of these while they are on offer.

Smooth · 15 Oct 2007 at 11:14

rpstewart said:
There was an interesting post on StorageReview a while back, it may actually be Vista that's indirectly providing better write speeds from onboard RAID5 solutions. It's all to do with Vista placing the start of a partition in a different place to XP and how that interacts with the stripe size of the RAID array. On XP you're guaranteed to have to do a load of extra parity processing because of the mismatch between the partition start and the stripe, with Vista if you get the stripe size right the number of calculations is vastly reduced.

Could you link me to the post, I had a look but I can't find it.

rpstewart · 15 Oct 2007 at 11:42

http://forums.storagereview.net/index.php?showtopic=25786

Mr Jack · 15 Oct 2007 at 12:04

Smooth said:
So if I had a decent mobo with IHC9R I could achieve atleast a minimum of 80mb/s in RAID5?

I think so, yes, I would not claim to be an expert though.

stoofa · 15 Oct 2007 at 14:10

However RAID 5 will never be as quick as other RAID solutions with regards writing speeds due to the way RAID 5 works.

RAID 5 is predominantly a server solution because it is the Read performance that is important.
If you're looking for performance on a workstation RAID 5 isn't the way to go.

Mr Jack · 15 Oct 2007 at 14:23

stoofa said:
However RAID 5 will never be as quick as other RAID solutions with regards writing speeds due to the way RAID 5 works.

True, it's slower than RAID0, but it is faster than a single drive and for an equal number of drives faster than RAID1+0/0+1 (but with less redundancy, obviously).