N5200 slow read but fast write over windows network

[mgaertne]

Hello,
since this is my first post, let me quickly introduce myself. I'm a networking specialist, working as a self-employed "öffentlich bestellter und vereidigter Sachverständiger" which is roughly translated, an expert witness.
My work involves frequently checking huge amount of data so I bought the THECUS N5200.

After sitting the thing up as RAID 6 (5 * 500GB Drives) and with firmware 2.00.04 in my network, I also experience very very slow reads.
The config:
1. Thecus is attached with 1Gb/s on a Cisco 2940 Switch. All clients are attached to 100Mb/s. Everything is full duplex
2. I use NFS and CIFS on the same folder
3. When using NFS I can write with about 10Mbytes/second, which is all that I can expect with NFS over TCP on a 100Mb/s-link. Same ballpark figures for writing with a Windows XP-Client and CIFS
4. When reading the data, thie NFS-Client reports less that 1 Mbytes/s (ONE large 600Mbytes File copyied to /dev/null), The CIFS-CLient will read 8Gbytes (a mix of large and small files) in about 45 minutes!

5. Filecaching is OFF on the THECUS
6. NFS-Parameters for mounting are rsize=8192,wsize=8192, CIFS is unchanged

Can anybody help me?
Oh, btw. The imgdup-module can't be enabled, SYSUSEER and SSHD are there and running

Mathias
PS: I also do miss the snapshot-window :-(

[omega]

Mathias,

My N5200 is connected to a 1GBit switch and my SuSE Linux 10.3 workstation too.
I'm using firmware 2.00.04.

When I mount a NFS share without any special options the transfer of a single 700 MB file (from the N5200 to the Linux machine using dd if=/mnt/... of=/dev/null) takes place with about 40 MB/s.
When I set rsize and wsize to 8192 the transfer speed decreases to about 28 MB/s. Dunno know why it is like this as I assumed just the opposite.

Anyway, I get much much better transfer speeds than you.... so I think it must be something special to your setup.

Just some ideas what you might want to check:
1) Check the duplex and speed settings for the N5200, the switch and the client.
2) Check the output of netstat -s for retransmits, network errors, etc.
3) Try a analysis with wireshark

Hope you'll find it.

Andreas

[mgaertne]

Hello Andreas,
well, I'm in touch with the thecus support on this.
What I've found out so far is
a) duplex-settings are not an issue here
b) memory size of switch port memory is not an issue here
c) Out of unknown reasons, I now can read! big files with appropriate speed with nfs, but
d) writing files, especially smaller files in a row (i.e with tar) are painfuly slow.
e) analysis with wiresharks clearly shows two oddities
- the thecus box always have a window-size maxed at 2xxx bytes (don#t remember offhand the
xxxes); I'd expect a max of 64K, especially if only one client is working with it
- The linux-box uses this window-size and sends three tcp frames with 1500,
1500 and 1056 bytes (ethernet-length used here). After tthe second frame, the required ack is not sent by the thecus.
After a timeout, the second frame is resent by the client; resulting in an immediate ack of the
second AND third frame.
Reading with CIFS, I could not check at the moment...

What really puzzles me is the fact that the thecus shows such a small window-size.
This really happenes when using small files to transfer, I guess the overhead of creating a new file is too much for the box...

Mathias

Mathias,

My N5200 is connected to a 1GBit switch and my SuSE Linux 10.3 workstation too.
I'm using firmware 2.00.04.

When I mount a NFS share without any special options the transfer of a single 700 MB file (from the N5200 to the Linux machine using dd if=/mnt/... of=/dev/null) takes place with about 40 MB/s.
When I set rsize and wsize to 8192 the transfer speed decreases to about 28 MB/s. Dunno know why it is like this as I assumed just the opposite.

Anyway, I get much much better transfer speeds than you.... so I think it must be something special to your setup.

Just some ideas what you might want to check:
1) Check the duplex and speed settings for the N5200, the switch and the client.
2) Check the output of netstat -s for retransmits, network errors, etc.
3) Try a analysis with wireshark

Hope you'll find it.

Andreas