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High RAM Usage during transfert on a nas (but not on 2nd)


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Hello !


I have a problem with high RAM usage during a transfer on my NAS 1.

On my NAS 2 the problem doesn't appear.


When I transfer via SMB a 10GB file for example, the RAM usage on my NAS 1 increase from 22% to 80% !

After the transfer, the RAM decrease to the normal value (22%), but sometimes the RAM stay at 80%.

If I do the same thing on my NAS 2, the RAM stay at 22% all during the transfer.


Can you tell me why on the NAS 1 the RAM increase during a transfer ?

Because after some hours, the speed of the transfer decrease until 5MB/s instead of 100MB/s...

To have again 100MB/s I have to reboot the NAS :sad:


Nb : when I connect on my NAS 1 via SSH, nothing tell me why the RAM usage is high... all the process use around just 0.5% of RAM as you can see in the screens.


Picture 1 : RAM usage at 89%




Picture 3 : The sum of the process use at most 20% of RAM and not 89%!



Pictures 4 et 5 : "htop" et "top" Command on terminal (we can see that lot of RAM is used but not by the processes




Picture 6 : The swap use just around 50 MB of the RAM, so it seem to be not the swap.



Thank you very much in advance for your help!

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2 other possible causes of High RAM usage (besides file encryption Enabled), is the RAID activity itself, for example RAID5, RAID6 and similar setups will use more RAM for processing of the strip/hash/disk spread. While RAID10, RAID1, and RAID0 is straight write.


Another cause which more or less relates to the above, is a slow overall PC, like older generation CPU, and older generation hardware that are not fast enough to catch up to the network card.


Basically the NIC card is pulling in data so fast, it's saturating the PCI channels, which in turn saturates the RAM / buffer, due the slow CPU is still processing previous batches.


This last part is very easy to test, if you say copy 1 GB data, and it writes it all to the NAS quickly without dropping speed, then it's good for small batches of data transfer.

then repeat the same test with a large batch of data say, copy 5GB of data, and if the NAS can write it quickly without dropping transfer speed then you can repeat the test with a 10GB data transfer until you figure out how much the system can handle per batch.


Since you mentioned earlier that 10GB uses a lot of RAM, perhaps the hardware can't keep up with large transfers, but might still work well with smaller amounts.


I've observed the Exact same behaviour with legit Synology DS210+ boxes when small amount of data is not using much RAM and transfer fast, but as soon as I copied larger amount of data, then I see high utilization of RAM and CPU.


Newer Synology boxes behaves more or less the same except for the beefier systems like the DS1815+

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