4 Disk RAID 0 Question

[Numbr]

I'm putting together a SCSI 160 RAID 0 array. I would like to keep it under $1000. All 4 channel adapters I have seen cost upwards of $700, so that route is out of the question.

So...

For maximum performance, should I go with 2 disks or 4 disks on a 2 channel adapter?

Also, I havent had much luck in finding benchmarks comparing SCSI RAID adapters. Any suggestions on where I could find some info or recommendations on which adapter would be best is greatly appriciated.

 

[jheine]

I think you got that mixed up with a IDE RAID interface. SCSI will support up to eight devices per channel (the controller card counts as a device). In a dual-channel card, you can hook up 15 more devices. SCSI drives are not limited to master/slave. You can put all four on one channel as long as they're addressed differently (more likely 0,1,2, and 3). What ensues then is whether you want software or hardware RAID. If you chose software, the average SCSI card will do. Hardware is definately more pricey, but may give you slightly better performance, especially in a 64-bit (PCI-X) version.

Jarrett

 

[HammerBot]

Yes. Make sure how many individual drives you actually can connect to the controller, before ruling out the 2 channel version.
You really should consider putting those drives in a RAID-5 array. If you get a decent controller, it most likely supports it.

<i><b>Engineering is the fine art of making what you want from things you can get</b></i>
<A HREF="http://www.btvillarin.com/phpBB/viewtopic.php?t=655" target="_new">My systems</A>

 

[Ncogneto]

Simple question. What makes you think you need a 4 drive RAID 0 SCSI array? Bragging rights?

Also, I havent had much luck in finding benchmarks comparing SCSI RAID adapters.

Thats because most high end raid cards are not designed with RAID 0 performance in mind. It levels like RAID 5 and 01 etc etc that seperates the men from the boys here. As for info you could browse the forums at storage review and 2cpu but prepared to get flamed when you tell them you plan on running a 4 drive raid 0 stripe.

It's not what they tell you, its what they don't tell you!

 

[mbetea]

As for info you could browse the forums at storage review and 2cpu but prepared to get flamed when you tell them you plan on running a 4 drive raid 0 stripe.

hehe, true, too true.

cdrw, floppy drive, cd-rom? what are these strange words you speak of?

 

[Numbr]

I realize that ultra/wide scsi can support up to 15 drives per channel. Although, when connecting more than one drive per channel, those drives have to share the bandwidth of that channel, which has a negative impact on the performance of each drive. So, with performance in mind, one drive per channel would be ideal.

Im not especially concerned with data loss due to 1 of the 4 drives failing. The RAID0 array would only be used as a scratch disk(for video editing) as well as the "drive" my OS would be running on. If I have a drive failure, big deal. I'll curse a little bit, get a replacement disk and then re-install. No permanent damage done. I could even do a nightly disk image onto a regular old IDE drive if I didnt feel like re-installing.

All I would like to know is...

Would read/write speeds and seek time be better or worse with 4 drives instead of 2 on 2 channels?

 

[mbetea]

what type of editing? (what type of streams are we talking about here?)

cdrw, floppy drive, cd-rom? what are these strange words you speak of?

 

[Numbr]

non-linear...
with primarly After Effects and Premiere

 

[Ncogneto]

Would read/write speeds and seek time be better or worse with 4 drives instead of 2 on 2 channels?

First of all in terms of seeks there would be no difference.


The second part will very depending on the hardware. Are you plannning on running the card on the 32/33 mhz bus? If so, with current state of the art drives you will more than saturate the bus, so you would be defeating the purpose of using 4 channels.

The RAID0 array would only be used as a scratch disk(for video editing) as well as the "drive" my OS would be running on.

When you speak the term "scratch disk" I am assuming you mean space allocated for your swap file. Ideally you would be better served loading up on the system RAM and not needing any swap.

As for running both your OS and using the array for your video editting this might not be the best route either. OS IO activity and video editing IO activity tend to exist on entirely different ends of the spectrum in terms of the size of file transfers they typically deal with. Optimizing for one will to some degree penalize the other. Another option might be with 4 disks to have two striped sets, one with your OS and another in which you use for video editing and perhaps your swap (which is better than having your swap and you OS residing on the same disk).

What I am getting at is you have X amount of dollars budgetted for equipment for your system to do the task at hand in the best possible way possible ( taking your budget into consideration). There is a very good chance that your money may be better spent and perform this task better in a slightly different route. Not knowing your equipment at hand I wouldbe inclined to suggest the following:

1) More system RAM
2) A 15k 3rd gen SEAGATE SCSI Drive (18 gig)for your OS
3) 2x 10k SCSI drives (several would work here) RAID 0 for video editing
4) A good dual channel controller of your choosing. Here you could even cut cost by doing a software stripe of the 2 10k drives. Your going to pay threw the nose for a quad channel controller for features that you will not even use, why not spend that moeny elsewhere?

It's not what they tell you, its what they don't tell you!<P ID="edit"><FONT SIZE=-1><EM>Edited by ncogneto on 12/11/02 03:34 PM.</EM></FONT></P>

 

[mbetea]

type of streams, what are we talking about here? dv uncompressed? analog mpeg2? unless you're running an outfit where outputting to HDTV or film resolutions, it would be a lot wiser to spend the money on other areas. i cap, edit, print to tape on 3 sperate 60gb drives, no raid, just the drives. never lost a frame. and by making an array and throwing OS, swap file, scratch disks and expecting to capture to it too is going to defeat the purpose you wanted the array for.
cdrw, floppy drive, cd-rom? what are these strange words you speak of?

 

[jheine]

I have to agree with ncogneto. Mind you, I'm now seeing what I can improve on with my own audio rig, but it is recommended by some manufacturers (Pinnacle comes to mind) that you have separate drives for OS and video data. Also, you could probably put at least two drives on a U160 channel and not saturate it.

If you can, post the system specs your running (or planning to run). It'll help us point you in the right direction.

Jarrett