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Network performance drop during rsync

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Pitfrr

Neophyte Sage
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Feb 10, 2014
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989
Hello,

I experienced a drop in network performances and I'd like to understand, so maybe someone has a clue to help me out.

- Context:
I have 2 FreeNAS boxes:
  • Main server: Xeon e3-1220 with 16GB of RAM, a supermicro X9SCM, 6x4TB RAIDZ2 running FreeNAS 9.2.1.8 (no jails, CIFS shares)
  • Backup server: AsRock C2750 with 16GB of RAM and 6x2TB in RAIDZ2 running FreeNAS 9.10.2 (no jails, CIFS shares)
The network looks like:
Network.png


Gb switch: Netgear GS108e
Mb switch: ADSL modem

rsync is running from the main to the backup server.
Of course, I have a transfert rate of about 10MB/s (due to the 100Mb/s network link). That's to be expected.
Both servers don't have a very high load ( top shows around 14% for rsync for each server).
So far it's all fine...

- Issue:
But when I start to use the PC (that is on the 1Gb/s network) and access to the main server, the response times are dramatic: the shares (CIFS) are very slow to browse, transfer rates drop to 1,6MB/s. I would not have expected that.

And an other surprise is that when I do the same on the backup server (i.e. access from the PC to the backup server), the response times are fine and I get 10MB/s transfer rates (i.e. saturation of the 100Mb/s link).

- Question:
How can this behaviour be explained?

My feeling is that maybe the 1Gb/s switch doesn't handle well the mixing of 100Mb/s and 1Gb/s links... that would be a pity? :-O Or could it be the 100Mb/s switch?
I don't think it is linked to rsync but that is when I experienced these performance drops.


- Work around:
When I put both servers (and the PC) on the same 1Gb/s network, everything is great... rsync is working (at around 70% on each server) and I get transfer rates around 70-100MB/s, which is fine.

Thanks for your opinions.
 

Ericloewe

Not-very-passive-but-aggressive
Moderator
Joined
Feb 15, 2014
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My feeling is that maybe the 1Gb/s switch doesn't handle well the mixing of 100Mb/s and 1Gb/s links...
It's vaguely possible, but I haven't seen that in person.
- Work around:
When I put both servers (and the PC) on the same 1Gb/s network, everything is great... rsync is working (at around 70% on each server) and I get transfer rates around 70-100MB/s, which is fine.
Honestly, that's going to be the fix, not just a workaround. GbE is cheap and a simple 5-port switch can be bought for less than 20 bucks.
 

Pitfrr

Neophyte Sage
Joined
Feb 10, 2014
Messages
989
Yes, definitely, the workaround has become a fix! :smile:
(with the advantage of a faster backup but that wasn't an issue)
 
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