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Alex Gerulaitis
Pegasus2: "superfast"?
on Dec 20, 2013 at 10:49:54 pm

I loved the look of them, very "pro".



The 8TB R4 box for $1.5K? It's also cheap. (Not so much with R6 and R8 versions though.)

"World's first Thunderbolt2 storage" - would be a nice match to newer Macs and MacBooks.

...and CNet also calls them "superfast".

Looks good, cheap, superfast? Sign me up.

Then I looked at how exactly "superfast" they are.

According to CNet:
- Pegasus 2 R8: under 400MB/s r/w in RAID5. Similar systems post over 700MB/s.
- Pegasus R4 (TB1) - 320MB/s reads, 190MB/s writes. That's underwhelming.

Anyone knows why Pegasus2 was so (relatively) slow in Cnet tests? Nearly twice slower than competition? Were there any other tests that posted better numbers?

-- Alex Gerulaitis | Systems Engineer | DV411 - Los Angeles, CA


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Alex Gerulaitis
Re: Pegasus2: "superfast"?
on Dec 20, 2013 at 11:20:51 pm
Last Edited By Alex Gerulaitis on Dec 20, 2013 at 11:39:40 pm

Perhaps CNet reviews just weren't done right.

Anandtech's 2011 review of Pegasus R6 has some very respectable numbers: 674 and 684MB/s read/write when empty, slowing down to 423 and 463MB/s when full.

In RAID0 - almost 780MB/s. With SSDs - 1GB/s.

Pegasus2 R8 should only be faster.

CNet should re-do their testing... ;)

Also, this page (in Japanese) has videos and images showing Pegasus2 benching 800MB/s writes and 700MB/s reads.


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Bob Zelin
Re: Pegasus2: "superfast"?
on Dec 22, 2013 at 5:48:25 pm

As you know Alex, current 8 bay thunderbolt 1 chassis are getting these speed results. So the damn Tbolt 2 chassis BETTER BE FASTER when they are actually released. Who knows how they are doing the testing.

Bob Zelin

Bob Zelin
Rescue 1, Inc.
maxavid@cfl.rr.com


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Alex Gerulaitis
Re: Pegasus2: "superfast"?
on Dec 23, 2013 at 2:25:32 am

Amen to that, Bob.

There's a limit what you can do with eight spindles in terms of speeds, and on top of it, Promise won't put a $1K RAID brain into that box... or SSD caching... That said, we can probably rely on our friends at AnandTech to take it apart, put it back together and test it with eight decent SSDs... :)


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Jon Schilling
Re: Pegasus2: "superfast"?
on Dec 23, 2013 at 10:46:08 pm
Last Edited By Jon Schilling on Dec 23, 2013 at 10:47:40 pm

Alex,

So, what you're saying is to invest another $3K in 8 SSD's to get the performance you should (theoretically) be getting?

Jonathan Schilling
Vertical Sales Manager
Proavio Storage by Enhance Technology Inc.
12221 Florence Ave.
Santa Fe Springs, CA 90670
Dir: 562-777-3498
Main: 562-777-3488 X106
Fax: 562-777-3499
Email: jon@proavio.com





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Alex Gerulaitis
Re: Pegasus2: "superfast"?
on Dec 23, 2013 at 11:09:24 pm

[Jon Schilling] "So, what you're saying is to invest another $3K in 8 SSD's to get the performance you should (theoretically) be getting?"

To saturate the 20Gbs TB2 bus - maybe - but how many people need that? Except perhaps the pure sport of benchmarking - and 4K DPX previews.


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Ricardo Reyes
Re: Pegasus2: "superfast"?
on Dec 24, 2013 at 12:22:41 am
Last Edited By Ricardo Reyes on Dec 24, 2013 at 12:26:30 am

We're seeing 800MB/s with 10Gb/s TB1 righ now, so I expect about 1280MB/s with 20Gb/s TB2.

So even with SSD's you'll still be limited.

Ricardo Reyes
Areca Technologies - US Channel
Ricardo@ArecaUS.com
http://www.Areca.com.tw

***** RAID is not a substitute for proper and regular backups *****



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Ricardo Reyes
Re: Pegasus2: "superfast"?
on Dec 24, 2013 at 12:13:45 am
Last Edited By Ricardo Reyes on Dec 24, 2013 at 12:51:19 am

From Cnet review:
"When I tested the original Pegasus R6, it was by far th fastest external storage device. Now the Pegasus2 R8 has almost double the speed"

So the Pegasus R6 was doing about 180MB/s? Come on, something has to be wrong with the way there testing. I hope....

Promise lists the Pegasus2 R8 is using desktop 4TB 5900RPM drives, but still don't expect it to be that slow. Slow, but not that slow.

Would I trust desktop drives to store 32TB of storage in a RAID environment? No way! But that's another story.

Ricardo Reyes
Areca Technologies - US Channel
Ricardo@ArecaUS.com
http://www.Areca.com.tw

***** RAID is not a substitute for proper and regular backups *****



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Chris Murphy
Re: Pegasus2: "superfast"?
on Dec 30, 2013 at 7:18:46 pm

Yes that R4 article needs an editor. Even after some minutes of "WTF moments" I still end up not sorting out what it is saying. But it still lacks test method details.

I read that the R4 self read/write (duplicating a folder) was 100MB/s. And transfer from an R6 to R4 was 240MB/s. Yet the 2nd graphic shows the R4's separate read/write performance as 170MB/s and 150MB/s. This makes exactly zero sense. How does it have 150MB/s write performance, and yet the R6 to R4 transfer was 240MB/s during which ostensibly the R4 is writing? :confused:

The R4 comes with 4 drives and RAID 5, which is how it was tested. The R4 data sheet says "up to" 800MB/s performance, and these numbers are well short of that. The data sheet says these are 7200RPM SATA drives. So we should see sequential reads in the vicinity of just under 3x the single drive read performance for full stripe reads (which may not be a real world test). A single Hitachi Ultrastar 7K4000 benches at 172MB/s average (maybe as low as 110MB/s for the inner zones), so yeah the article reports confusing performance. But then we don't know their test method, or even Promise's.

The test method is quite important, especially with RAID. If the test method doesn't mimic actual workflow, the results can be skewed so badly as to be useless.

Worth a separate thread, if it doesn't already exist, is what the range of video production workloads look like, and what's typical or average (if there is such a thing). I suspect a very common workload is sequential read only, but then there's also sequential read and write - but I don't know if that looks like a folder duplication operation or something else. I'm also not familiar with the various file formats and how they contain video files, if they're really one large file or if they're smaller files in a container that looks like a file. Also relevant is how much metadata is being produced. Concurrent read/write seems like a worst case scenario for RAID, but maybe that's the typical workload. There is a high performance penalty when there aren't full stripe reads and especially for writes.


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Eric Hansen
Re: Pegasus2: "superfast"?
on Jan 3, 2014 at 6:33:44 pm

Alex, you bring up an interesting point with 4k DPX. Since the new Mac Pros are geared toward 4k production, and could have awesome speed in Davinci, how would you propose building a DPX cache for the nMP? Perhaps putting SSD PCIe cards in multiple Thunderbolt enclosures and putting them in a Software RAID0? Im guessing that since each enclosure could saturate the 20Gb/s connection, and the Mac Pro has three TB2 controllers, would each SSD have to be placed on a different TB2 controller to achieve max speed?

Or would you recommend this particular Resolve user just jump to a Linux setup?

These are fun times!

e

Eric Hansen
Production Workflow Designer / Consultant / Colorist / DIT
http://www.erichansen.tv


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Alex Gerulaitis
Re: Pegasus2: "superfast"?
on Jan 3, 2014 at 7:27:29 pm
Last Edited By Alex Gerulaitis on Jan 3, 2014 at 7:38:58 pm

How large and how fast does it need to be? Any chance of using the internal SSD?

Otherwise, I'd think so, striping 2-3 boxes across TB channels should do it - something someone will eventually test - until then we won't know for sure... :)

nMP specifically designed for 4K is just the usual Apple BS... excuse me, marketing. Sure it supports 4K displays (yay!) - does it support the full VFX pipeline in terms of performance and bandwidth? Let's wait and see on that.

An ATTO 12G SAS controller was benching 5.5GB/s with 16 SATA SSDs at the last NAB on a Z820 - so in the rectangular world, it seems to be easily achievable. :)

(That said plain vanilla 4K (uncompressed RGB 2160p24 12-bit) is still manageable at around 500MB/s although once you get to multiple streams, higher fps or higher res (8K, 14-bit, etc.) - there's no saying.)


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Chris Murphy
Re: Pegasus2: "superfast"?
on Jan 3, 2014 at 10:48:47 pm

FusionIo PCIe flash is at 1.5GB/s per card. Not accounting for encoding, yes two in a raid0 will saturate one TB2 controller.

I haven't tested Core Storage "fusion drive" in anything other than a consumer type workload. If a read results in a cache hit, then you get SSD read speeds. If it's a cache miss, you'd get the raid speed. The write speed would always start out at SSD speed, but for video this would end quickly (within 4GB of writing) as Core Storage doesn't aggressively migrate data off the SSD. This might be enough to moderate the slow ramp up Bob Zelin reported elsewhere... maybe. But just like raid0, if the SSD drive dies, kaboom to all data, not just what was on the SSD.

Bcache on Linux shows some promise, as it does have some knobs unlike Core Storage, but it's a bit early to support in production. However, it's mainly write through for sequential writes, so that will avoid the SSD. Whereas any random io caused by metadata writes (?) would hit the SSD and at least not reduce performance on the raid made of HDDs. Those random IOs hit the SSD in write back mode, get aggregated, and written sequentially to the HDD. But then, on linux there are other options like Infiniband which probably obviate the need for a local SSD cache anyway.


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Alex Gerulaitis
Re: Pegasus2: "superfast"?
on Jan 6, 2014 at 9:35:34 am

[Eric Hansen] "how would you propose building a DPX cache for the nMP? "

Here is one option:

LaCie Little Big Disk Thunderbolt 2, allegedly 1.4GB/s, consisting of dual 500GB PCIe SSDs in RAID0 in a TB2 box.


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Eric Hansen
Re: Pegasus2: "superfast"?
on Jan 6, 2014 at 7:37:42 pm
Last Edited By Eric Hansen on Jan 6, 2014 at 7:39:44 pm

Thanks Alex. Macrumors quoted an article that briefly tested 2 of these enclosures in a RAID-0 and got 2GB/s Write and 2.4GB/s read. So yeah, that could work. Basically four PCIe SSDs spread over two TB2 connections.

Seems nuts to need that kind of speed, but I could see some of my 4k grading clients needing this. Since most 4k acquisition is raw and compressed (Redcode, F55), this wouldn't be necessary for that footage. But for VFX shots in DPX, OpenEXR or TIFF, this could help. It could also help during export and DCP creation. It would also help if Resolve ever added the pre-cache feature that Baselight has (ie, if you have Redcode footage, it's debayered and cached before you need it in grading, so the system can used the cached shot and doesn't have to redebayer every time you manipulate a grade, so you don't need a Red Rocket)

But then it makes me wonder what the latency of TB2 is compared to direct PCIe

e

Eric Hansen
Production Workflow Designer / Consultant / Colorist / DIT
http://www.erichansen.tv


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