I was beginning to suspect this myself, having seen the
website already.  But Spectra Logic's own website lists both the
compressed and uncompressed speeds as 32MB/s.  I'm starting to think
they just lie on their site.

On Jun 24, 8:10 pm, Charles Chou <[EMAIL PROTECTED]> wrote:
> 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.
> Regards,
> 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 -- Hide quoted text -
> - Show quoted text -
You received this message because you are subscribed to the Google Groups 
"open-iscsi" group.
To post to this group, send email to
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at

Reply via email to