Hi Michael,

The spec on NAStape 250 says the transfer rate is 16MBps:


I think it is most likely the target, the enclosure in this case, that 
is slowing things down. The native transfer rate for LTO4 is 120MBps and 
LTO3 at 80MBps. I have tested LTO3 drive with HiFN's Sypher iSCSI box 
and got 56MBps with 256K writes. This is with encryption on. Passthrough 
speed was even faster. I was using open-iscsi and dt so I don't think 
open-iscsi is at fault for the low performance you experienced.

Charles Chou

Michael wrote:
> Thanks for the suggestions.  Everything you suggested checked out.
> Speed is definitely 1000Mb/s, no errors, and hard drive speed is
> plenty quick.  Also, the tape drive itself isn't iSCSI, the enclosure
> is (Spectra Logic NAStape 250).  Any other suggestions?
> On Jun 18, 8:07 pm, Sparqz <[EMAIL PROTECTED]> wrote:
>> 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.- Hide quoted text -
>> - Show quoted text -
> >

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