[Beowulf] SSD caching for parallel filesystems

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Mon Feb 11 17:51:48 PST 2013

Jim Lux

-----Original Message-----
From: Vincent Diepeveen [mailto:diep at xs4all.nl] 
Sent: Monday, February 11, 2013 4:32 PM
To: Lux, Jim (337C)
Cc: beowulf at beowulf.org List
Subject: Re: [Beowulf] SSD caching for parallel filesystems

> I was responding to your question asking for an example of  
> something needing high bandwidth and small storage, but that  
> couldn't be adequately addressed by just buying a ton of  
> conventional RAM.
> These systems don't have a CPU.. it's just disk drive, FIFO, data  
> converter.

You're speaking here of a very specific NASA type problem.

>>> not really.. In reality NASA doesn't do much of this.  The defense industry does quite a bit more.  I would guess that the number of people building wideband signal simulation/record/playback systems is comparable to the number of people building clusters with SSDs.. they're both niches with probably in the range of 1000 firms at that kind of scale.  Maybe half a dozen companies building the systems, the rest just using them.  

It's like asking why one would design shoes for the guy who manages  
to jump 10 meters high - and then you show up with an astronaut 10+  
away from now who might jump on the Moon 10 meters high :)

> I suspect digital video recorders are another application.. very  
> similar kind of usage..

> You stream raw video in at some Gbytes/second and just dump it to  
> the drive(s). digital motion picture projectors at 4K resolution  
> are probably another example.  Although there, you are looking at  
> fairly large data sets.

Not at all, you just want petabytes of storage there.

>>>> see the example of high resolution digital movie cameras.. no petabytes, but needing GByte/second kinds of transfer rates
>>>> Another example would be digital projection in movie theaters.  Distribution on SSDs might be cheaper than distribution on conventional hard disks: fewer drives needed to get the rate to supply the projector, and makes the distribution costs cheaper (shipping costs are less on a smaller box).  They're not looking Petabytes here either.  A few 10s of Terabytes, I would imagine.  

> The RED cameras stream to flash, SSD or conventional drives, for  
> instance.  9Megapixels/frame*30 fps is 270 megapixels/second.
> The newer EPIC cameras do 31.8Mpix/frame * 96 fps...    I think  
> they run about 400-500 Mbyte/sec to a SSD "magazine"
> The film business is used to interchanging magazines. A typical  
> 35mm cine camera has 400 ft and 1000ft magazines.  At the usual  
> 24fps, that works out to about 1 foot/second, so 400 or 1000  
> seconds of shooting time.  A comparable RED/EPIC magazine, then,  
> probably holds half a terabyte or so.
> http://www.red.com/store/products/redmag-4-pack
> Here you go.. a 4 pack of 256GB drives for $9100...

This is embedded hardware, again not some HPC type workload.

>>> You didn't ask for HPC workload.. you asked for widebandwidth, small storage..

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