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DPS Quatrus board with Huge U320

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Michael AndersonDPS Quatrus board with Huge U320
by on Dec 11, 2003 at 1:22:30 am

Hello fellow Grazers,

A few weeks ago I took it on as "personal challenge" to get our new U320 disk array to sustain 4 streams with the Quatrus board. We now have it running in the lab, and hope to get confirmation from DPS in the next few weeks. I think this small 5 drive array will set a new price/performance point for Quatrus storage.

Best Regards,


Michael H. Anderson
Chief Engineer
Huge Systems


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Lyn NorstadRe: DPS Quatrus board with Huge U320
by on Dec 12, 2003 at 2:07:40 pm

[Michael Anderson] "I think this small 5 drive array will set a new price/performance point for Quatrus storage. "

Michael -

What size drives are you using with the Quattrus?

Regards,
Lyn


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Michael AndersonRe: DPS Quatrus board with Huge U320
by on Dec 12, 2003 at 4:08:12 pm

Hi Lyn,

The drives are 250GB IBM/Hitachi drives, though all models down to 120GB seems to work OK now.

Best Regards,

Michael H. Anderson
Chief Engineer
Huge Systems


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Andrei MihailescuRe: DPS Quatrus board with Huge U320
by on Dec 12, 2003 at 6:18:07 pm

[Michael Anderson] "A few weeks ago I took it on as "personal challenge" to get our new U320 disk array to sustain 4 streams with the Quatrus board. We now have it running in the lab, and hope to get confirmation from DPS in the next few weeks. I think this small 5 drive array will set a new price/performance point for Quatrus storage. "

That's great news, Michael. But are those 4 streams compressed or uncompressed?

And when you say "with the Quattrus board" I assume you mean it's connected directly to the integrated U160 controller, right?

Cheers,
Andrei Mihailescu


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Michael AndersonRe: DPS Quatrus board with Huge U320
by on Dec 12, 2003 at 7:38:37 pm

Hi Andrei,

Four streams, uncompressed, connected directly to the integrated U160 SCSI port. One stream at the beginning of the disk, two in the middle, and one at the very inside. It's run overnight several times.

Best Regards,


Michael H. Anderson
Chief Engineer
Huge Systems


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Lyn NorstadRe: DPS Quatrus board with Huge U320
by on Dec 12, 2003 at 8:33:27 pm

Michael -

And how does the performance compare to, say, two 15k Cheetahs connected directly to the Quattrus?

In other words, what kind of data rate are you seeing?

Regards,
Lyn


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Michael AndersonRe: DPS Quatrus board with Huge U320
by on Dec 12, 2003 at 10:20:28 pm

Hi Lyn,

Do you mean benchmark performance or application performance? Application wise, both the Cheetas and our U320 product connected directly to the Quatrus will run 4 streams of uncompressed video. I haven't looked closely at benchmark performance, but if you would like, I could compare the two.

Best Regards,


Michael H. Anderson
Chief Engineer
Huge Systems


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Michael AndersonRe: DPS Quatrus board with Huge U320
by on Dec 12, 2003 at 10:34:30 pm

Hi Lyn,

Just ran the performance plot. The 15k Cheetas show about 70MB/Second at the OD dropping to about 45MB/Second at the ID. Our U320 (5 IBM/Hitachi 250GB drives) shows a flat 47MB/Second across the whole surface.

Both systems look like they can sustain 4 streams of uncompressed SD.

Best Regards,

Michael H. Anderson
Chief Engineer
Huge Systems


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Lyn NorstadRe: DPS Quatrus board with Huge U320
by on Dec 12, 2003 at 10:52:25 pm

[Michael Anderson] "Just ran the performance plot. The 15k Cheetas show about 70MB/Second at the OD dropping to about 45MB/Second at the ID. Our U320 (5 IBM/Hitachi 250GB drives) shows a flat 47MB/Second across the whole surface. "

Michael -

Yes, thanks. That's the data I was looking for.

I believe that would be 'per drive' data for the Cheetahs, as the DPS hardware test doesn't test as a stripe set.

Regards,
Lyn




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Michael AndersonRe: DPS Quatrus board with Huge U320
by on Dec 13, 2003 at 1:15:00 am

Hi Lyn,

My guess is the performance of this test won't actually go up with a stripe set anyway. It looks like it generates interleaved IOs that attempt to span the disk surface, then computes some mathematical average of the data rate. Four streams of SD is around 80MB/Second, though the test results show only 47.

Have you ever hear the expression "There's lies, terrible lies, and then benchmarks"?

But a useful test, none the less.

Best Regards,

Michael H. Anderson
Chief Engineer
Huge Systems


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Andrei MihailescuRe: DPS Quatrus board with Huge U320
by on Dec 13, 2003 at 5:06:08 pm

[Michael Anderson] "Four streams, uncompressed, connected directly to the integrated U160 SCSI port. One stream at the beginning of the disk, two in the middle, and one at the very inside. It's run overnight several times. "

So the 5-drive unit is seen as a single drive by the Quattrus board? A dual-channel U320 RAID-0 unit stripped with the Quattrus tool would probably saturate the U160 interface, right?

I also assume the 5-drive unit was configured as RAID-0, right? Do you think there is a chance that a bigger unit will work at the same performance level configured as RAID-50/30 for data redundancy?

Thanks,
Andrei Mihailescu


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Michael AndersonRe: DPS Quatrus board with Huge U320
by on Dec 13, 2003 at 7:18:23 pm

Hi Andrei,

I apologize in advance for my long winded answer:

First, yes, this is a single 5 drive U320 unit that is hardware striped and appears as one drive to the Quattrus.

Concerning "saturating" the U160 bus with two units, here's what I've seen:

The Quattrus generates very nice IOs. They appear to be a field size (about 300k), with little or no variation. When a timeline is started, the Quattrus prefetches it's own internal buffers, then generates IOs for each stream as it needs it. This appears as "semi-random" IOs to the storage device, though in fact they are multi-stream sequential.

For recording data, the Quattrus negotiates an 80MB/second data rate. For playing data, it negotiates a 160MB/second data rate. This is the rate of the data when it's actually moving. To compute the available data rate, you have to take a ratio of the time data is moving divided by the total "wall clock" time, which includes BUS FREE phases, Artibration, Selection, Command and Status phases. Hence the total theoretical rate is some large fraction of 160MB/Second. In my analysis, both the Cheeta drives and our drives have a net "potential" rate of about 100MB/Second.

So from what I've seen, playing 4 streams of uncompressed video achieves about 80% of the total available data rate (80MB/Second produced divided by 100MB/Second available). My guess is adding another unit will only provide a margin performance improvement. I.E., the bus is almost saturated with a single unit.

To be totally fair, the Cheeta drives are a little more effecient on the bus than the Huge disk array, so their total available data rate may be higher. However, the Huge disk array generates almost 300MB/Second internally to a 64MB cache buffer, and has a very intelligent multi-stream read ahead algorithm. So in practice, I think the performance is roughly equivalent.

The big difference is cost per GB. The Cheeta drives are much more expensive. I paid $600 for an 18GB Cheeta. The raw drive cost of a 180GB IBM/Hitachi is about $140. That's a 40 to one advantage. Even after I add my box, my electronics, and make some profit, I would guess there will be a 5 or 10 to one cost advantage to the end user. Also, five 180GB drives have the storage capacity of 50 18GB Cheeta drives, so the package is a lot smaller, requires a lot less power, and is much less likely to fail.

As for RAID3/5 functionality, I haven't focused much on the Quatrus with RAID3/5 yet. A question for Quattrus users:

Are you looking for redundant storage?

Best Regards,


Michael H. Anderson
Chief Engineer
Huge Systems


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Andrei MihailescuRe: DPS Quatrus board with Huge U320
by on Dec 13, 2003 at 9:53:47 pm

Michael, thanks for the insight into the inner workings of the Quattrus. No need to apologize, it's definately very interesting - Leitch provides some basic information about this in the User Manual, but they certainly don't go into such details.

[Michael Anderson] "The Quattrus generates very nice IOs. They appear to be a field size (about 300k), with little or no variation. When a timeline is started, the Quattrus prefetches it's own internal buffers, then generates IOs for each stream as it needs it. This appears as "semi-random" IOs to the storage device, though in fact they are multi-stream sequential. "

It does makes sense, afaik the stripping part of the Quattrus drive management system during capture basically just writes Field A to Drive 0, Field B to Drive 1, Field A to Drive 2, etc. until it goes back to Drive 0 (depending on how many drives are in the stripe set). This being the reason why they say that stripping more than 2 drives together doesn't give you any increase in practical performance.

[Michael Anderson] "So from what I've seen, playing 4 streams of uncompressed video achieves about 80% of the total available data rate (80MB/Second produced divided by 100MB/Second available). My guess is adding another unit will only provide a margin performance improvement. I.E., the bus is almost saturated with a single unit. "

You are most likely right. I was thinking that maybe adding a second unit (or using a dual channel unit) would give more "tolerance" to seek time issues, when you have very short (different) clips cut together on the timeline. From what I understand, this would be a worst case scenario for IDE-based drive arrays.

As Quattrus is limited to 4 SD streams, I guess there isn't much point anyway in having much more than that available - it's useless. Unless Leitch will manage to squeeze some more performance out of their boardset with software/firmware upgrades. For instance by allowing 4 streams each with alpha channel - atm this is not possible afaik because of the DVE resources of the 3D module. This would push the total data rate requirement very close to the 100 MB/Second limit that you mention.

[Michael Anderson] "The big difference is cost per GB. The Cheeta drives are much more expensive. I paid $600 for an 18GB Cheeta. The raw drive cost of a 180GB IBM/Hitachi is about $140. That's a 40 to one advantage. Even after I add my box, my electronics, and make some profit, I would guess there will be a 5 or 10 to one cost advantage to the end user. Also, five 180GB drives have the storage capacity of 50 18GB Cheeta drives, so the package is a lot smaller, requires a lot less power, and is much less likely to fail. "

Well, to be fair, atm a 73.4 GB Seagate Cheetah 15K.3 is around $570, and the 18 GB version is just under $200. The prices have fallen quite a bit in the SCSI world lately. Altough I am sure that an unit such as Huge's would still be (much) cheaper overall, especially in the case of 300 GB+ storage capacities.

[Michael Anderson] "As for RAID3/5 functionality, I haven't focused much on the Quatrus with RAID3/5 yet. A question for Quattrus users:
Are you looking for redundant storage? "


Can't speak for the others, but yeah, I would be interested in that. Right now because of space issues, we just finish the projects and back them up on external drives or just print them to our tape archive. If we would upgrade the total storage space, we would be more inclined to keep the projects online for a longer time (and possibly even forgetting to make backups - such is life!).

Not to mention that even now I worry that if a drive fails during a very important project, we loose everything. Even with Batch Recapture, it would be quite annoying and potentially very costly. So if we could upgrade to both larger and redundant storage, it would be extremely useful... just as long as the total cost to do that isn't prohibitive.

Cheers,
Andrei Mihailescu


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Michael AndersonRe: DPS Quatrus board with Huge U320
by on Dec 13, 2003 at 10:40:32 pm

Hi Andrei,

Thanks for straightening me out about 15k Cheetah costs, it looks like I paid WAY too much! Fortunately, I only bought two. Have you ever heard the expression "You can buy better, but you can't pay more!"? Looks like that's what I did.

I'll take a look next week and see how to integrate our RAID functionality into the Quattrus environment. FYI, our U320 RAID unit should retail for about $4k/TB.

Best Regards,

Michael H. Anderson
Chief Engineer
Huge Systems


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