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LunarMist

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Just like my other NSA units the write speed is always faster than the read speed. I never can understand the rationale for that. Regular drives always have faster reads than writes.
 

sdbardwick

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Just like my other NSA units the write speed is always faster than the read speed. I never can understand the rationale for that. Regular drives always have faster reads than writes.
B/c on writes, in some situations, you are limited by the interface to cache transfer rate, rather than the physical media transfer rate for reads. Depending on the number of drives, RAID implementation, and size of on-disk cache, you can maintain a higher write speed for an extended period of time.
 

LunarMist

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But why is the interface or other performance bottleneck asymmetrical in the opposite way from the conventional wisdom that reads are faster than writes?

The QNAP 10GbE card in the NAS is wired directly to the 10GbE Intel adapter in the computer, but I also tried a Quantia 10GbE adapter in the PC and there was no difference. I even tried the Quantia in the QNAP, but it is not recognizable and I'm not about to figure out how to add the drivers to the QTS. I also put the Intel 10GbE in the QNAP and that connects fine with the Quantia in the PC. The bottom line is that the performance is all the same.

I am using a simplified setup with RAID 6, EXT 4, no storage pools or Snapshots and no M.2 cache. The write speeds are sustained at 500-600, depending on the source. The OS cannot be caching anything, because it stayed about the same for over 14TB, when I terminated transfer manually. Read speeds are 400 or so.

The NAS and drives are quite cheap and literally twice as fast as the backup unit it will replace, so I'm not complaining.
I just want to understand the reason as it has been bugging me for several years. I don't think it is a coincidence since the behavior is the same with two QNAP and one Synology NAS, all being different models with different kinds of CPUs/chipsets.
 

LunarMist

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For some reason the QNAP take forever to boot. This one requires five minutes and announces the status in a synthetic female voice.
Synology units take about 1.5-2 minutes to boot. It's not a matter of CPU, just QNAP mentality. I'll probably leave the NAS on and live with the ~40W power drain.
 

DrunkenBastard

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Going to try out the Synology DS920+, on special on Prime day for $439. Will use 500 GB 970 Evo nvme drives for cache, and bump ram to 8GB.
 

Handruin

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That sounds like a decent setup for the money and nice that it has a cache option via nvme. What size HDDs will you be adding to it?
 

DrunkenBastard

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The Seagate Exos drives seem quite affordable (14TB for $285) but apparently they are third party via Amazon and a lot of people are getting serial numbers that come back as OEM.

The WD Gold 12 TB is $384.

i have three external 8TB WD enclosures I got a few years ago when they were on special for $129 or $179, I might just shuck them and go with three 8s to start. Also looks like RAM can be expanded to 20GB total with a 16GB so-dimm.
 

DrunkenBastard

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Ended up going with two WD 12TB easy store drives from Best Buy with store pickup. I dont like to expose them to UPS/Fedex handling.
 

DrunkenBastard

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So the way the cache works on the 920, with one nvme drive it is restricted to read cache, with two nvme drives it mirrors them and enables read and write caching. However you can't then mount them as a seperate drive. It can only be assigned as cache to a single specific volume. Hopefully DSM 7 will allow that in the future.

Basically silent running in terms of fan noise, drive seeks are the only sound it makes.
 
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