# Gigabit switch speeds



## NBPk402 (Feb 21, 2012)

Can anyone explain why I am getting low speeds, and then spikes on my LAN? When I look at my transfer speed in Windows I am getting 10Mb/s average. I have a Cisco Business Gigabit switch. The data was going from my windows mapped NAS drive to a USB SSD. I know the first question you will ask is why is it using a mapped drive. Well I have had a problem that periodically appears, and appears to be when Microsoft does its updates... I originally was able to view my NAS in Windows, until one day it no longer showed up in Windows 7. I have had multiple installs of Windows (from formatted HDDs), and every time the drive is there and then with time disappears. So right now I have been without Windows seeing my NAS for a couple of months on a 4 month install of Windows 7. 


Do I need to have a SSD for caching from my NAS, and also a SSD on my PC to get the speeds up (as you can see I get bursts of over 900Mb/s)?


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## robbo266317 (Sep 22, 2008)

The most likely explanation is that the data is being cached before writing to the drive, the cache fills up since the drive has a much lower write speed and then you get another burst when the cache is near empty.
If you look at the blue line on the disk activity it drops both times just before the network bursts.

What is the write speed of the SSD?


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## theJman (Mar 3, 2012)

I wonder if the numbers Windows provides are accurate; the 900 mbs burst speed is about twice the physical transfer rate of USB 3, so unless there is some caching mechanism I'm instantly suspicious of the performance rating.

FWIW... there's nothing wrong with having the connection be a mapped drive. For some applications, that's the only way they can actually see the storage.


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## NBPk402 (Feb 21, 2012)

robbo266317 said:


> The most likely explanation is that the data is being cached before writing to the drive, the cache fills up since the drive has a much lower write speed and then you get another burst when the cache is near empty.
> If you look at the blue line on the disk activity it drops both times just before the network bursts.
> 
> What is the write speed of the SSD?


Transfer Rate: 450 MB/s


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## NBPk402 (Feb 21, 2012)

theJman said:


> I wonder if the numbers Windows provides are accurate; the 900 mbs burst speed is about twice the physical transfer rate of USB 3, so unless there is some caching mechanism I'm instantly suspicious of the performance rating.
> 
> FWIW... there's nothing wrong with having the connection be a mapped drive. For some applications, that's the only way they can actually see the storage.


The problem I have seen on my setup is that if you use a mapped vs actual the speed is slower.


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## Tonto (Jun 30, 2007)

No idea, have you tried the MS help forum? Those guy are pretty savvy.


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## mgittelman (Jul 10, 2013)

You don't need SSD caching for your NAS. SSD caching is usually only good for non-sequential data transfer and can hurt performance of transferring single large files due to the overhead of trying to write to the cache and read from it at the same time.

What kind of NAS is it? Many are CPU constrained even though they have gigabit interfaces.

Things to check:

Are you sure your USB SSD is both USB3 capable and connected to a USB3 port? USB3 does 5Gb, while USB2 is limited to 480Gb.

What is the speed at which you can transfer files from the NAS to your local hard drive on your computer (not the USB one)?

Download lanspeedtest and test against a SMB share on your NAS. This will bypass the read/write restrictions on your local PC.

Run CrystalDiskMark on the USB drive to verify it supports the write speeds you are expecting.

Assuming all this is being done wired (and not wireless) cross connect the NAS and your computer directly with private IP addressing to bypass any problems that might be cropping up in the Cisco switch.

Any other computers you can test to see if they have the same issue with the NAS?


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## NBPk402 (Feb 21, 2012)

mgittelman said:


> You don't need SSD caching for your NAS. SSD caching is usually only good for non-sequential data transfer and can hurt performance of transferring single large files due to the overhead of trying to write to the cache and read from it at the same time.
> 
> What kind of NAS is it? Many are CPU constrained even though they have gigabit interfaces.
> 
> ...


USB is a USB3 Hub, and the SSD is also a USB3. I am running Unraid for my NAS (DIY i7). Everything is hardwired and going through my Cisco SG200-26 Gigabit Ethernet Smart Switch with 24 10/100/1000 Ports and 2 Combo Mini-GBIC Ports (SLM2024T-NA). My other devices are all Kodi Media boxes (various brands)so I have no way to test them. I will need to get the software and report back for the rest of the info.

tia,
Ron


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