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stublehustle

Should I use NVME drive for cache?

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I recently upgraded my gaming machine so my old motherboard an asrock x97 extreme 6 is now my new unraid board. I now have a Samsung 950 pro nvme m.2 256GB drive on the motherboard that currently isn't doing anything. I currently have a 850 EVO 500GB as my cache drive.

 

The question I have is should I use both the drives in combination for cache or just the NVME? I do not have any plans for any type of a VM on this machine so I wouldn't need to save it for that. 

 

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Your choice, just keep in mind if you use the default settings, you will end up with only 256GB of space on the cache pool if you use the 256GB drive with the 500.

 

You don't give any information about how you use your server, whether you have dockers or plugins that would benefit from the speed, whether you leave info on the cache that might benefit from a pool. So, in light of the info not given, nobody can give you an informed answer.

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If you do plan on using NVME, I would choose a solid brand.. IE, samsung, corsair, intel.. something worth its salt. Didnt see the samsung in the first post.. Need coffee *EDIT*

 

Also, be sure to edit the default 'mover' settings. By default IIRC, its once a day it moves files from the cache, to the array. 200-500 gigs fills pretty fast.

 

Final note, NVME speeds can be in excess of 3gbps as seen with the samsung 970 pro. This can easily saturate most peoples arrays (7200 rpm = give or take 100-200 mbps per drive, and as this is UNraid, not raid, you don't get the benefit of striping across multiple drives (at least not in the same way) which can and will bring your array to a stuttering halt.) *look for sawtooth patterns in file copies as an identifier*

 

Given a choice, I would use matching 2.5 inch ssd's in raid0 or 1, and save the NVME for something more useful. Dockers/VM's for example, might be a better choice, and not as bad on the r/rw iops. 

 

Final, Final note..

I wouldn't mix the 2 drives (nvme, sata) for a cache array. One is rated for 2000+ mbps, other is 750~ mbps. (Not that you would see a difference, both of them independently would probably saturate your entire array)

 

Edited by tbonedude420
lack of coffee.

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On 8/31/2018 at 3:59 AM, stublehustle said:

I recently upgraded my gaming machine so my old motherboard an asrock x97 extreme 6 is now my new unraid board. I now have a Samsung 950 pro nvme m.2 256GB drive on the motherboard that currently isn't doing anything. I currently have a 850 EVO 500GB as my cache drive.

 

The question I have is should I use both the drives in combination for cache or just the NVME? I do not have any plans for any type of a VM on this machine so I wouldn't need to save it for that. 

 

Can you? Sure. Should you? Unlikely.

 

The underlined statement suggests you have a 2nd machine that for sure can benefit from having a fast NVMe SSD. Using your NVMe for unRAID cache (and only cache) is a massive waste and given the 256GB size also a massive inconvenience because it will fill up super quickly.

 

 

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Question. Hello everyone. I am a really new to this and building a UnRaid system. I wanted to use a 1tb nvme ssd as my cache drive. I am building it primarily as a Plex Sever. Going to run 8 @ 8tb WD red drives and a 1 @ 10tb as a parity drive. Will the cache drive work for this build or I’m I better off using a 2.5 1tb ssd. Thank you in advance for the help. 

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One thing to think about is if you're doing any docker automation on NVME, most setups will move those files from the NVME then to the cache and then to the array.  Thus, you are decreasing the lifetime of both flash drives simultaneously, whereas if you just went to NVME for the whole thing, it would be one write because of the way moves on file systems work within a drive.  I am currently considering doing a dual NVME CACHE in RAID-1 setup to get around this.  It's so expensive to get decent endurance ratings on these things, so this is another way to help with that (for me at least).

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