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PostPosted: Mon Feb 02, 2009 1:02 pm 
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Joined: Sun Feb 08, 2004 7:18 pm
Posts: 562
Location: Austin
I migrated a node from Fremont to Dallas last night. As with pretty much everything at Linode, the process was extremely smooth, in fact it's amazing how easy it was.

The only issue I had was that it took quite a while to transfer the data. The maximum throughput rate was something like 1.8MB/s, which means it took around 2 hours to transfer my ~12GB node. Since I had to begin this procedure in the dead of night, it was kind of a pain.

Over a 100Mbit link, it should have taken something like half an hour. I believe the slowness is caused by SSH. Some of the buffers hardcoded into the default SSH cause serious bandwidth underutilization over high-speed, higher-than-LAN latency links.

Here's some research on this topic, including a patch: http://www.psc.edu/networking/projects/hpn-ssh/

I think it's at least worth looking into. Thanks!


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PostPosted: Mon Feb 02, 2009 1:14 pm 
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Joined: Tue Apr 15, 2003 6:24 pm
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Website: http://www.linode.com/
Location: Galloway, NJ
Actually, we're already using those patches. With additional tweaks and customizations and those patches, we were able to improved same-DC migration speeds by 10x!

Unfortunately, inter-DC migrations go through the Internet, where we have no control over routes and link speeds. I'm afraid there's nothing more we can do.

-Chris


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PostPosted: Mon Feb 02, 2009 2:05 pm 
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Great. I just wanted to make sure there wasn't anything being left on the table. Thanks for being on top of things.


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PostPosted: Mon Feb 02, 2009 4:48 pm 
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Joined: Sat Feb 10, 2007 7:49 pm
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Website: http://www.arbitraryconstant.com/
caker wrote:
Unfortunately, inter-DC migrations go through the Internet, where we have no control over routes and link speeds. I'm afraid there's nothing more we can do.
Zero the empty space, pipe it through gzip. 8)


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