What causes this?

tangoseal

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transfer is from a Sata SSD (Kingston 1TB Enterprise Dc400) to 1tb Nvme (Phison based e12 - blazing fast nvme)

Curious what is causing this sharktooth kind of transfer

1598656893348.png
 
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Dec 1, 2011
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Probably:
  1. Initially, all data goes into the receiving SSD's cache, which can ingest it very fast.
  2. Cache fills, performance takes a dive as now data has to be written directly to TLC NAND while the SSD simultaneously drains its cache.
  3. Cache space opens up some and begins accepting data, allowing the transfer to accelerate.
  4. GOTO 2.
Also, this is a gigabit ethernet link? Then that graph's numbers are somewhat suspect, as theoretical max is 125 MB/s, real-world a bit less.
 

SamirD

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Probably:
  1. Initially, all data goes into the receiving SSD's cache, which can ingest it very fast.
  2. Cache fills, performance takes a dive as now data has to be written directly to TLC NAND while the SSD simultaneously drains its cache.
  3. Cache space opens up some and begins accepting data, allowing the transfer to accelerate.
  4. GOTO 2.
Also, this is a gigabit ethernet link? Then that graph's numbers are somewhat suspect, as theoretical max is 125 MB/s, real-world a bit less.
Yep, what I said with more details. :D

I don't think this is over a gigabit link at all as the initial copy is much, much faster and exceeds gigabit bandwidth by a large margin. :eek:
 
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Yep, what I said with more details. :D

Yeah, you ninja'd me in response.


I don't think this is over a gigabit link at all as the initial copy is much, much faster and exceeds gigabit bandwidth by a large margin. :eek:

That's why I asked. It's been edited, but I'm certain OP (tangoseal) originally stated a 1 Gb/s link. May have been a typo and was supposed to be 10 Gb/s? Or maybe a "gigabit NIC" inside a VM, which can actually transfer between VMs much faster?
 

tangoseal

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To all asking I apologize, I have no idea why I even mentioned networking.

This is internal SATA to NVME on same physical machine. I was just moving a VM container around and noticed completely weird sawtooth like network performance.

I am using a Microcenter Inland Premium nvme 1TB that was pulling from a 1TB Kingston DC400 Enterprise SSD which both have cache internally and are extremely high performing in their respective classes.

There was zero networking involved. I am just tired and made a total mistake when I was typing my description.
 

Nobu

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Yep, extremely quick read to cpu/memory, then write to cache, then you are either cpu/memory limited, disk write limited, or bus (sata I/II/III, PCIe) limited.
 

tangoseal

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Yep, extremely quick read to cpu/memory, then write to cache, then you are either cpu/memory limited, disk write limited, or bus (sata I/II/III, PCIe) limited.

I rebooted and notice that it stopped doing it. Now it runs full Sata III speeds as the SSD is capable non stop. That was weird. Maybe some other software was hindering performance? Time to investigate.
 
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