[OpenAFS] Re: WAN speed

Jeffrey Altman jaltman@your-file-system.com
Thu, 22 Mar 2012 16:16:38 -0400

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On 3/22/2012 3:43 PM, jukka.tuominen@finndesign.fi wrote:
> Hi all,
> here are some ping results outside LAN:
> 1.62  1.80  1.62  2.33  1.69  1.64  1.75  2.35  5.77  3.85  4.69  2.73 =
> The internet speed is the same 100/5.
> I just moved ~20M/~2000 files
>   AFS to SSH server ~220KB/s
>   SSH server to AFS ~80KB/s
> The client was in WAN this time, whereas both servers where in the same=

> LAN (not sure it they knew it :).
> br, jukka

On average your files are 10K.  10K is smaller than both the RPC
chunksize and the window size.  For each read or write of a file there
will be a single RPC.

The big difference is going to occur due to directory operations.  When
writing to AFS you are going to issue a CreateFile RPC for each file
entry.  When you read from AFS you are going to issue one
InlineBulkStatus RPC for each 50 entries in the directory.  In other
words, 2000 RPCs when writing and 400 RPCs when reading.

Ping times are not representative of baseline RPC latency nor will they
include client side file system overhead for the two different execution

You will see very different results if you read and write a single 20MB
file or even a 1GB file.  For maximum throughput with large files and
the OpenAFS master source code branch you can use a window size of 254
and a chunksize of 8MB.  Increasing the window size and the chunksize
have no impact when the file sizes are small as they are in your test.

Jeffrey Altman

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