Question NAS ssd caching vs drive caching

Jun 19, 2019
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Hi all,

Just purchased a used QNAP TS-453BT3 for video editing and the original owner had installed two 256gb M.2 drives for caching.
At the moment, I'm shopping for drives to populate the NAS and am wondering how much of a practical difference will exist between a drive that has 128mb vs 256mb cache, since the NAS already has onboard caching.
It's totally possible I've misunderstood something and the two types of cache have nothing to do with each other - I'm a noob at this NAS stuff.

Thanks for the replies!
Andrew
 

USAFRet

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Right, these have nothing to do with each other.

The 2x M.2 drives are a fast preliminary space for data, prior to writing to the other spinning drives in the system.
The 128 or 256MB cache on an individual drive is relevant to that drive only, and makes no significant difference either way.
The cache existing in the NAS is again different...:)

I have an earlier version of that, the TS-453a. 4x 4TB Seagate Ironwolf drives.
What other drives are you planning to put in it?
 

Satan-IR

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Apr 18, 2014
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Hi, welcome to the forums!

What drives do you plan to get/use? If your usage, video editing, means accessing large chunks of data sequentially (which I think it does) having a larger cache is not that much of a benefit/plus.

If the system is usually/always busy (reading/writing data) and if the slower media (assuming HDDs) are indeed a bottleneck to the operation of the system/NAS; I'd say having a larger cache MIGHT be a bit beneficial if a subset of the data is accessed repeatedly or if even a smaller part is accessed randomly.

In your case, video editing, it also depends on the data transfer rates you usually need. For example editing 1080p and 4K are different stories. Although nature of video editing I think requires sequential reads/writes.
 

USAFRet

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Also, as always, performance is dictated by the slowest device in the chain.

Here, it would be your LAN interface between the PC and the NAS.
The drives, even spinning drives, are much faster.

Unless your PC also has a 10Gbe network adapter or the relevant Thunderbolt port, you're at typical 1gigabit LAN speed.
 
Jun 19, 2019
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Thanks for the great info.

I'm looking at Ironwolf or Red drives, 8 or 10TB. Trying to keep it below $1k and depending on what sales are(n't) happening, selecting 256MB over the 128MB might break the bank. However, speed is everything and I'm willing to pony up if performance is noticeable.

I'm also unsure as to where the bottleneck would occur, though I suspect it would be the NAS CPU, at which point, I'd have to ask how much of a difference would exist between 5400 and 7200 drives.
I'm currently running on an i9-9900k, 64GB 3200 ram, Nvidia 1070. More here: https://pcpartpicker.com/user/andrewsciba/saved/8qXxGX

Thanks!
 
Jun 19, 2019
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Hi, welcome to the forums!

What drives do you plan to get/use? If your usage, video editing, means accessing large chunks of data sequentially (which I think it does) having a larger cache is not that much of a benefit/plus.
Thanks!
So the editing that I do typically involves 4k footage, but it's not sequential - I'll pull from 10 different video files over a 20 second section of timeline, similar with the audio.
 

Satan-IR

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Thanks!
So the editing that I do typically involves 4k footage, but it's not sequential - I'll pull from 10 different video files over a 20 second section of timeline, similar with the audio.
No problem. In that case I think the main bottleneck would be the bandwidth as USAFRet said and that'd mainly be the network/LAN bandwidth.

Also if I'm not mistaken I think you're looking at 90MB/s for each 4K stream. If the numbers you said is comprised of you pulling from 10 different files, one at a time, to put in 20 second timeline I don't think the total size would be as high as to really bottleneck with the drives (especially if you do a fast RAID). Unless you need to constanly pull from all those files, as streams, simultaneously all the time. Then the network bandwidth is an issue to consider.

As USAFRet said above, you're at the mercy of the LAN throughput more or less. If the bandwidth is so high as to saturate the ordinary LAN bandwidth you might need a 10GB NIC/switch and the SSD cache doesn't really come into play in this. In that case, again as USAFRet said, you might need NICs with thunderbolt support some of which are basically designed/made with video editing in mind.

At the end of the day I'd suggest you wait and ask @USAFRet to kindly have his input when he has the time.
 

USAFRet

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Editing is not the same as playing/streaming. Editing and rending to disk is not 'real time'.
So while the LAN may be the limiting factor, it does not really hinder your editing efforts.

The playback after editing is all one stream, not multiple segments. And the Qnaps WILL do 4k playback over the LAN, just like any other 4k capable device.

Even going back a couple of years to my TS-453a, it states it will do 4k transcoding on the fly. I don't have a 4k display, so I can't truly verify.
But the NAS CPU would not seem to be a big limit, even how they appear to be 'weak'.

How much RAM is in your Qnap? I upgraded mine to 16GB. Even though it states 8GB is the max, it appears to recognize the entire 16GB.
 
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