Slow transfer speed due to SSD cache acceleration

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cryptochrome
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Re: Slow transfer speed due to SSD cache acceleration

Post by cryptochrome »

It's really quite astonishing to see that years after the caching feature was introduced, and years after the issues with it have first been reported, this utter piece of crap software is still not working. The SSD cache works fine for anything that's happening *on* the device, but if you use it as intended, you know, as a *network* attached storage, the cache craps out. And as usual, Qnap is neither listening nor interested. But they have the audacity to still advertise the feature.
pokrakam
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Re: Slow transfer speed due to SSD cache acceleration

Post by pokrakam »

Five years to be precise...
Furyous
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Re: Slow transfer speed due to SSD cache acceleration

Post by Furyous »

I can confirm it is still happening on my TVS-951X OS 4.5.4.1741
muckmuck
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Re: Slow transfer speed due to SSD cache acceleration

Post by muckmuck »

Has anyone tested cache acceleration after upgrading to QTS 5.0?
TVS-882, 32 Gig, 6x3TB, 4x500Gig SSD
TS-253 Pro, 8 Gig, 2x6TB
Furyous
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Re: Slow transfer speed due to SSD cache acceleration

Post by Furyous »

muckmuck wrote: Tue Oct 05, 2021 9:23 am Has anyone tested cache acceleration after upgrading to QTS 5.0?
Seems to be better but I only tested once
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galosu82
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Re: Slow transfer speed due to SSD cache acceleration

Post by galosu82 »

I did some testing today.

I used:
  • MacBook Pro (16-inch, 2019) with macOS 11.6
  • QNAP TVS-672XT i3 + 32 Mb RAM + 6x 6TB WD Red Pro HDD + 2x 1TB Samsung SSD 970 EVO PLUS
  • Sonnet Echo Express SE IIIe Thunderbolt 3 enclosure + Sonnet 1 GbE PCIe card
I connected the MacBook Pro to the NAS via both a Thunderbolt 3 cable and a CAT7 Ethernet cable.

And these are the results...


=====


Reading/writing directly from/to SSDs (RAID 0)


Thunderbolt 3 connection

Image


10 GbE connection

MTU 1500

Image

MTU 9000

Image


===


Reading/writing directly from/to HDDs (RAID 6)


Thunderbolt 3 connection

Image


10 GbE connection

MTU 9000

Image


===


Reading/writing from/to HDDs (RAID 6) with read/write SSD caching enabled (RAID 1)


Thunderbolt 3 connection

Image


10 GbE connection

MTU 9000

Image


=====


SSD caching is not crucial when it comes to transferring big files. That's clear.

But, apparently, the major issue is that Thunderbolt 3 connection is not working as expected at all.

If you are experiencing similar poor performance, I recommend you to submit a ticket to QNAP support here: https://service.qnap.com/en/user/create-ticket
cryptochrome
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Re: Slow transfer speed due to SSD cache acceleration

Post by cryptochrome »

Forget about submitting tickets to QNAP. They are utterly and completely useless. I had opened probably dozens of tickets regarding the broken Thunderbolt as well as the broken caching to no avail and with no results. You might as well talk to a brick wall.
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galosu82
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Re: Slow transfer speed due to SSD cache acceleration

Post by galosu82 »

Further testing…


=====


PC with Windows 10 <-- Thunderbolt 4 connection --> QNAP TVS-672XT with SSD cache ON

Image


MacBook Pro with macOS 11.6 <-- Thunderbolt 3 connection --> QNAP TVS-672XT with SSD cache ON

Image


=====


I really don't understand where the problem originates.
cryptochrome
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Re: Slow transfer speed due to SSD cache acceleration

Post by cryptochrome »

The interesting part here is: How is your cache configured? The problem this thread addresses only occurs with "cache all I/O" or setting cache block sizes larger than 512KB (results may vary, but it definitely breaks down with block sizes large than 1 MB). That's the caching issue.

Your Thunderbolt issue (which I also have, by the way), is not really related to the cache. It could be an incompatibility between macOS's propriatary SMB implementation and SAMBA on the QNAP. I have long switched to a 10 GbE connection between my Macs and the QNAP. It's slower than Thunderbolt theoretically is, but due to the problem it's a hell of a lot faster that the broken Thunderbolt implementation. Tat being said, Thunderbolt is not really what this thread is about.
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galosu82
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Re: Slow transfer speed due to SSD cache acceleration

Post by galosu82 »

cryptochrome wrote: Mon Oct 11, 2021 5:13 pm The interesting part here is: How is your cache configured? The problem this thread addresses only occurs with "cache all I/O" or setting cache block sizes larger than 512KB (results may vary, but it definitely breaks down with block sizes large than 1 MB). That's the caching issue.

Your Thunderbolt issue (which I also have, by the way), is not really related to the cache. It could be an incompatibility between macOS's propriatary SMB implementation and SAMBA on the QNAP. I have long switched to a 10 GbE connection between my Macs and the QNAP. It's slower than Thunderbolt theoretically is, but due to the problem it's a ** of a lot faster that the broken Thunderbolt implementation. Tat being said, Thunderbolt is not really what this thread is about.

Hello, cryptochrome. For sure, that issue is not exclusively related to the SSD cache. Anyway, my previous tests also highlighted something related to the SSD cache. The difference between writing on my RAID 6 HDD array with or without that cache is not big, but it is there.


My SSD cache settings are the following ones.


Image

Image
P3R
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Re: Slow transfer speed due to SSD cache acceleration

Post by P3R »

galosu82 wrote: Mon Oct 11, 2021 4:30 pm I really don't understand where the problem originates.
Bob Zelin that have plenty of experience also recommend against direct Thunderbolt connections. Do an Advanced Search (click the cogwheel in the upper right corner), here in the forum and do a search for the keyword "Thunderbolt" with the author "Bob Zelin" and read what Bob recommend.

Once you've fixed the Thunderbolt issue you have, then deal with the subject of this thread.
RAID have never ever been a replacement for backups. Without backups on a different system (preferably placed at another site), you will eventually lose data!

A non-RAID configuration (including RAID 0, which isn't really RAID) with a backup on a separate media protects your data far better than any RAID-volume without backup.

All data storage consists of both the primary storage and the backups. It's your money and your data, spend the storage budget wisely or pay with your data!
cryptochrome
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Re: Slow transfer speed due to SSD cache acceleration

Post by cryptochrome »

Try setting it to "Random I/O" and then select a small bypass block size. You will likely see much better results. I think there is a bug (and has been for years) that brings the caching to a crawl when the block size exeeds a certain amount. At least that's what I see on my end.
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galosu82
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Re: Slow transfer speed due to SSD cache acceleration

Post by galosu82 »

P3R wrote: Mon Oct 11, 2021 6:52 pm
galosu82 wrote: Mon Oct 11, 2021 4:30 pm I really don't understand where the problem originates.
Bob Zelin that have plenty of experience also recommend against direct Thunderbolt connections. Do an Advanced Search (click the cogwheel in the upper right corner), here in the forum and do a search for the keyword "Thunderbolt" with the author "Bob Zelin" and read what Bob recommend.

Once you've fixed the Thunderbolt issue you have, then deal with the subject of this thread.

Please read this post of mine: viewtopic.php?p=799973#p799973

I tested my read/write speed with and without SSD cache. My findings also highlighted a huge problem with Thunderbolt connection. But the main reason of my testing was the lack of performance increase after enabling SSD cache.
Last edited by galosu82 on Mon Oct 11, 2021 7:20 pm, edited 1 time in total.
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galosu82
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Re: Slow transfer speed due to SSD cache acceleration

Post by galosu82 »

cryptochrome wrote: Mon Oct 11, 2021 6:58 pm Try setting it to "Random I/O" and then select a small bypass block size. You will likely see much better results. I think there is a bug (and has been for years) that brings the caching to a crawl when the block size exeeds a certain amount. At least that's what I see on my end.

Thanks for the suggestion. Would that settings be beneficial also in a video editing environment where the files are quite big?
P3R
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Re: Slow transfer speed due to SSD cache acceleration

Post by P3R »

galosu82 wrote: Mon Oct 11, 2021 7:20 pm Would that settings be beneficial also in a video editing environment where the files are quite big?
With Bob Zelin being probably most experienced installer in the world of Qnaps for video editing usage I have to again refer to the recommendations made by Bob. For video editing he recommend against the use of a SSD cache in QTS. Apart from that he recommend as many 7200 rpm disks as the chassis have drive bays and a static volume. Bob say that will give you around 1000 MB/s with 10 GbE in a TVS-872XT.

Please look for his posts. He has been writing this many times.
RAID have never ever been a replacement for backups. Without backups on a different system (preferably placed at another site), you will eventually lose data!

A non-RAID configuration (including RAID 0, which isn't really RAID) with a backup on a separate media protects your data far better than any RAID-volume without backup.

All data storage consists of both the primary storage and the backups. It's your money and your data, spend the storage budget wisely or pay with your data!
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