Slow Download Speeds To NAS? Confused?

[buchanan0204]

When I download files (I'm using Ubuntu .iso for this e.g.) directly to my C: drive. It maxes out my connection 80Mbps. However, when I download the file directly to a mapped network drive it's a lot slower, anything from 50%-75% of the speed when downloading to local storage.

For some details:

NAS = Seagate Central NAS connected to a BT HomeHub 5 (Gigabit LAN)
Laptop WiFi = Intel AC7260 connecting at an average of 650Mbps

I've ran LAN Speed Test (program to measure network speed) and i consistently get results of 100Mbps+ transfer speeds to my NAS, which of course is greater than my internet speed.

To make things a little stranger. Usenet downloads can max out for a while before varying, however for the best part, they are maxing out.

Torrent downloads on the other hand are very slow when downloading directly to the NAS as opposed to local storage once again.

My internal network speeds are definitely greater than my internet speeds, so I see no reason why I shouldn't be able to max out my connection when downloading to the NAS.

I'm thinking the HomeHub 5 is the bottleneck?

Any suggestions?

[KeyboardDemon]

I think the bottleneck is down to the write speeds on the hard drive in the NAS unit and possibly the processor on the NAS.

[DanceswithUnix]

Agree with KeyboardDemon.

If you can mount a network drive from a quick PC on your network and try downloading to that, you should be able to prove if your network is OK.

Writing to the NAS can be much slower than reading from it, specially if you are doing RAID. From a quick Google it sounds like yours is a single drive model? This review found it wrote at half the speed it could read at: http://uk.hardware.info/reviews/4649...ormance-tester

If you are doing a torrent, then you are writing to multiple positions in the file so that compounds the problem.

[buchanan0204]

The write speed on the drive in the NAS is capable of around 30-35MBps. I am only downloading at 8-9MBps on my 80Mbps fibre connection.

I know the drive is able to write speeds in excess of 8MBps from my laptop by using Lan Speed Test.

I don't understand why downloading an Ubuntu .iso is much slower when downloading directly to the NAS as opposed being maxed out if downloading to local storage. Ignoring torrents for the time being, this is one large file and shouldn't be slowed like this.

If I copy a large 3GB file from my laptop, directly to the NAS. It sustains a 30MBps write speed.

I will try downloading onto a networked drive in a PC using a Gb ethernet connection with a Samsung Spinpoint 1TB drive in it.

[aramil]

Is the client doing the download running on the nas or the PC?

If it is on the PC it goes from the net to the PC where the client is (temp working folder/ram(ie client software), to be verified) then to the nas for storage, also if the client is remote (ie on the pc) it is also adding file pieces & checking this file constantly over your internal network.

You need to account for all this local network traffic / HDD read/writes as well.

Nb if you are allowing it to be seeded out from the client as well this would increase local network traffic to.

If the torrent client was on the nas you would not have this extra network chatter and two way data swapping over local devices.

[buchanan0204]

Is the client doing the download running on the nas or the PC?

I'm downloading an Ubuntu .iso using my laptop to a mapped network drive (Seagate Central)

If it is on the PC it goes from the net to the PC where the client is (temp working folder/ram(ie client software), to be verified) then to the nas for storage, also if the client is remote (ie on the pc) it is also adding file pieces & checking this file constantly over your internal network.

Really? I'm doubtful as I have downloaded 5GB files directly to the NAS when I had 200MB free local disk space. This is not the case now for the record, and the speeds were neither slower, nor faster when this was the case. I also never seen any drop in C: storage capacity when downloading. I don't think it uses the C: as temp storage before sending it over the network. I could be wrong of course.

You need to account for all this local network traffic / HDD read/writes as well.

I am sure there is nothing going on elsewhere in the network, no downloading, streaming etc. All other PC's and devices were turned off for testing. There is no other traffic.

Nb if you are allowing it to be seeded out from the client as well this would increase local network traffic to.

If the torrent client was on the nas you would not have this extra network chatter and two way data swapping over local devices.

I'm referring to an Ubuntu .iso downloaded directly from the Ubuntu website which downloads at full speed when downloading to local storage. No seeding going on here.

Thanks for everyones help so far. Once I get a chance. I'm going to download to a disk on a networked PC to eliminate the NAS.

[scaryjim]

I assume you're only connected to the home network by wifi? In which case your computer is effectively having to negotiate all the data across the wireless network twice - it downloads it to your laptop, then sends it back across the network to the NAS. There may be more than enough theoretical bandwidth, but I suspect consumer wireless hardware isn't great at handling the traffic routing necessary to simultaneously download and upload a file across the network...

[DanceswithUnix]

One other experiment that might be interesting would be to plug the laptop directly into the router, avoiding WiFi.

I don't understand why downloading an Ubuntu .iso is much slower when downloading directly to the NAS as opposed being maxed out if downloading to local storage. Ignoring torrents for the time being, this is one large file and shouldn't be slowed like this.

The reasons can be varied, but basically writing to something flat out is an easy and often well tested and indeed benchmarked case, so I would expect it to do well. Even under those conditions, it isn't really doing that well at 35MB/sec.

Writing to a device slowly is rather trickier. At what point does it stop waiting for more data and start writing to disk? If you wait too long, then you could lose data on power fail. So after a short wait you write the data. That does a sequence like:

- Write data to journal in case of power fail
- Write data to disk
- Update directory information with new file size and last written to date
- Mark work as done in journal.

While it is doing all that, more data comes in. If the NAS runs out of buffer ram for that data, then the PC writing to it stalls. That stalls the app on the PC doing the file transfer, which kicks in the network stack congestion control telling the sender out on the Internet to lower the tcp window scaling & slow down transmission so that data isn't lost.

If this is over WiFi, then there is a turn around time from receive to transmit and back which makes the whole thing more complicated.

You can simplify and tune the system, but sometimes the only thing you can realistically do is download locally and then write the finished download across the lan onto the NAS because that is faster.

[RoseGul]

I have no idea what to try next. Ubuntu rules out a driver problem in Windows and installing my old card it is enabled no problem. I can also enable and disable my old card using the function key shortcut. This does not work with the AC7260.






_____________________
Fai

[TeaLeaf]

It also depends if the NAS is trying to write e.g. Raid5 or ZFS etc. That will also slow down the max write speed.

[abaxas]

Multiple options......

1) you are downloading loads of torrents at the same time - disk thrash
2) torrent connections are not encrypted - isp throttling
3) torrent connections are encrypted - not enough oomph on nas (should be good for 20-50 mbps)
4) torrent port is closed on router so you can connect out but others cant connect in.
5) the torrent client is ****

[TeaLeaf]

5) the torrent client is ****

Succinctly put!