RAID should degrade video capture?Right?

[droolian01]

Hi there, hope this is too stupid a question.
I will be building a new system soon, and my main use at present for it will be video capture. Onboard RAID looks a very good idea for full frame no-drop capture, but the raid controller is just another pci device, so won't there be 'competition' between it and the capture card? If so, having a dedicated capture hd on its own ide channel is surely better than any raid set up.

I ask this as most performance figures for raid systems (simple ide stripping) use routine apps as a measure, whereas video capture (imho) is different as stated above.

thanks in advance.

[Neo Neko]

No RAID should be good. Whatever form of RAID you are using it is all controlled by the controller card. The data is sent to the controller card and it then directs it to the propper channels. So once the data hits the card it does not need to hit the PCI bus again for any reason. It is should not eat up bus time or cause problems. It should be a ready and awaiting funnel siphoning all the data your capture card could throw at it.

[movmasty]

yes, raid 0 should permit more writing bandwidth

http://www6.tomshardware.com/storage/01q4/011023/index.html

[kopelen]

Unless you have the WD1000JB or the WD1200JB 8MB cache version drives, RAID will definitely help decrease the amount of frame drops.

Software RAID is an alternative solution to creating RAID and is as good if not better than the onboard RAID on most motherboards. You will need Windows 2000/XP for software RAID.

[fisix]

the onboard hard disk controllers use the same pci bus the card slots do, so by using an addon raid card you won't be using any more of the bus than you did before. in fact, by using a really good raid card with lots of memory on it for it's own internal cache, you in fact might free up more of the bus time because it doesn't have to stall for write access as often when it writes to the array. i say 'might' because i'm not sure how the bus handles write access interrupts. shrug.

now, this is only the case if you use the right raid array, meaning the topology for speed rather than safety. a card with a large cache will speed things up a little over your normal onboard controller, but not usually enough to make a double backup topology appreciably faster than a single drive (many times it is actually slower on identical drives). the fast topology should give a marked increase in disk access (read/write) times.

i'd have to see some evidence that a software raid somehow worked smoother or faster than a hardware one, because up to this point i've seen evidence to the exact opposite, and since it sounds like you want to offload cpu work as much as possible, i think i'd nix a software raid solution. just buy a decent card. i hear the ones from promise are cheap and good. adaptec makes the industry standard raid cards, but their solutions have actually tested slower than cheaper competitors in the relatively new market of eide raid cards (i'm assuming you aren't going to be buying scsi drives).

the one caveat is that you have to install the card in a slot that doesn't have to share it's irq with anything, if possible. you can tell this from the mboard's manual. supposedly this doesn't matter with irq steering, but i'd do your best just the same. if there is the option to enable APIC in your bios, i suggest you enable it, but BE WARNED that if it isn't already enabled, you WILL HAVE TO RE-INSTALL win2k if you boot once with it changed (possibly true for win98). more than a few people have hosed their system unexpectedly by fiddling with the APIC option. be prepared.

-jig

[Scuba]

Another thing too often being forgoten it to increas the PCI sycls in the BIOS from the default 32 to 64.
Most new cards are using some type of PCI bridge and this small tweek help regulating the trafic on the PCI bus better.

Also several makers are releasing PCI performance enhancers (Pinnacle for example)
This tools are registry tweeks that can give the video capture card little more slack when it's trying to do it's work and give hit some more resurces over less important devices on the bus.

[kopelen]

Get a 'true' RAID add-on card that has a RISC chip and cache built-in to the card.

[droolian01]

Thanks everyone for the speedy and inteligent replies.
Everyone agrees that RAID will not 'compete' with the capture process, and all the tips will be extremely useful.
The general consensus seems to be that having on board RAID is possibly not the best solution (dedicated card with cache better). But as the cost of getting a mobo with onboard RAID is not much extra generally, i may as well do that and if i find i need more hd speed i can add a dedicated RAID card later, and use the onboard RAID as vanilla ide channels.

This should satisfy my upgrade urges for about a year, until i NEED to get hold of a clawhammer!!!
Thanks.