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What real-world transfer speeds should I expect for backups over my home network?

What real-world transfer speeds should I expect for backups over my home network?

I want to start backing up my home PCs (mix of XP and Vista) to a spare machine (XP).

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Guest [Entry]

"The network is going to be your bottleneck, a 100mbit connection has a maximum throughput of 12.5 MByte/second. So in ideal conditions you would see 45GByte / hr.

Of course real world conditions aren't quite ideal, depending on your network and devices you might see 90% of that throughput or 60% of that (or any other amount).

Wireless will of course be slower yet, plus the advertised speed is a bit of a pipe-dream. Ideal wireless connectivity means only one powered device talking to the router, no interferance from other RF devices (wifi shares the same spectrum of RF as most other wireless consumer devices, 2.4GHz).

There's too many variables to tell you what you can expect in terms of overhead. Provided your wired machines are in good working order, not under load, without other network activity, and with a decent switch between them and decent CAT-5 that isn't damaged, too long, coiled near anything that might emit high EMI, and properly crimped then you should see close to full throughput. Wireless is much more of a crapshoot. If you build a faraday cage and put both your hotspot and laptop inside it then you might get close to it's full throughput.

...long story short is to find a large file (30gb VM drive, 8GB ISO image, etc) and time its transfer.

The overhead you're seeing on small files is normal, and it's not unique to the network transfer. For example, unzipping 1 1GB file may take 90 seconds, whereas unzipping 1024 1MB files might take 180 seconds (the numbers are pulled from my backside).

I can't point a finger at a single culprit, but typically a large file on a non-fragmented drive is stored in a relatively continuous block--small files are likely to be scattered. This means that when the operating system wants to transfer files 1 thru 1000 it has to find the start of each file on the drive and seek to that location.

Transferring small files across the network might amplify the slowdown, in which case you would want/need to 'roll' them together into an archive using a tool such as Zip/Rar/Tarball/etc...

disclaimer the bottom-line that lots of small files are slower to move than a few large files is based on lots of experience--the specific reasons that cause this slowdown go beyond my knowledge, there's likely several factors beyond just the drive seek-time."