I must have really dark sunglasses on, because I've never seen an
iSCSI tape drive before?

Anyhow, I don't think your MTU (lack of jumbo frames) is the problem,
I can easily get 50MB/s sustained transfers over a gigabit network.

First I would confirm that the path between your linux iSCSI server
and your tape drive is running a the full wire speed (gigabit).

Assuming eth0 is the ethernet port you use for iSCSI traffic type
"ethtool eth0" and make sure you see:
        Speed: 1000Mb/s
        Duplex: Full
amongst the garbage that fills the screen.

Also, you can type "ifconfig eth0" and you should see something like:
          RX packets:62361505 errors:0 dropped:0 overruns:0 frame:0
          TX packets:110583510 errors:0 dropped:0 overruns:0 carrier:0
make sure that there are no errors (or dropped packets, overruns or
framing errors)

I wouldn't worry too much about the TCP Checksum messages that
wireshark shows (usually it's because another part of the system
checks these checksums and mangles them in the process)

Finally, can your local disk support 30MB/s ?  might be worth
installing something like iozone or bonnie++ to make sure your disk
can be read and written to at 30MB/s.

Hope this helps!

On Jun 17, 6:27 am, Michael <[EMAIL PROTECTED]> wrote:
> Hi all,
> I've been using open-iscsi to set up an IBM Ultrium LTO-4 tape drive.
> I can connect and transfer files and everything, but the maximum read
> or write speed I can get is like 16MB/s by tweaking the block size.  I
> am on a gigabit network, which the tape drive supports.  The drive
> specifications rate it at 30MB/s so I'm off by 50%.  Does anyone know
> what I can do to get the speed up to scratch?  I'm pretty much a Linux/
> network newbie so I no idea if its an open-iscsi tweak or a network
> tweak that I could possibly do.  Also, I checked and my network card
> only supports MTU=1500, if that matters.
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