Unfortunately no one can be told what fun_plug is - you have to see it for yourself.
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Hi every one,
I own a DNS-321 and a DNS-323, both "enhanced" with the fonz's amazing fun_plug (v 0.5). I also own a DIR-655 so my whole setup is gigabit (with brand new CAT-6A cabling, too).
I'm experiencing very low write speeds when copying data from one NAS to the other, using either scp or rsync. Very low, as in between 200 and 500 Kbs! But the performance of the units isn't abormal when I use my PC to upload, download or copy files (by drag and drop). I get a steady 10Mb when downloading, up to 20Mb when upload (DNS-323, a little less on the 321) and a steady 7Mb when using drag and drop between the two unit's shares. Overall, I'm very satidfied with that.
But I though I would get much faster writes if I were to copy straight from one NAS to the other...and I don't understand why I'm not.
Has anyone else experienced this? I know some of you out there use two units with rsync backups or similar...any ideas or explanations for this behavior?
Thanks,
Nicolas
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I don't have the setup so I can't be sure, but it strikes me that the speeds are about right.
Your gigabit setup has nothing to do with it. It is sort of like wondering why your 1957 VW bug can't do 200 MPH on a race track.
With scp you are asking the DNSes to encrypt and decrypt your data, which takes a lot of CPU power and the DNSes don't have a lot of that so things slow down. (And why do you need to encrypt data on a private network?)
The case is about the same with rsync, which in normal mode is setup to optimize not sending much data over what is expected to be a slow network. Again consuming time in the diffing and other parts of the protocol. To get the speed up somewhat use --whole-file option which doesn't try to send pieces of the file. But really understand where rsync shines and that is in the decision to only send what is changed. For instance is it better send GB of files that have not changed at a top speed or only the files (or parts of files) at slower speeds?
If you use cp or maybe ftp you should see the real speed and then you should be talking about performance that matches (somewhat) what sending using copy and past to your PC does. I say somewhat because in fact it still isn't the same. Your PC has a lot more power and speed and it is also probably caching some of the transfer in memory. With the DNS to DNS transfer you have to low power devices talking to each other.
BTW the above is why almost everyone suggests using cp/ftp or a PC to get two DNSes setup with duplicate data first before changing over to something like rsync to keep them up to data.
Last edited by chriso (2012-05-02 07:22:45)
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Thanks for the reply Chriso, and for taking the time to explain all of this.
I expect I will do as you suggested and copy the bulk from a PC while using rsync only to update.
Cheers,
Nicolas
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1. Install NFS-support (ffp), mount DNS-321's resource into DNS-323's filesystem.
2. Install rsync (ffp), use it with -a option (i use -ahHi)
I think transfer speed would increase up to 2-2.5 MB/sec
Best wishes...
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