Couple of questions around iSCSI

[Nick Howard]

I've been having a play around this week with how best to setup iSCSI and a couple of things threw me a little. I tested write speeds in a number of configurations as below:

Firstly my speeds to a CIFS share were averaging around 88 MB/s

PC to file extent (over the network) 320 MB/s
PC to file extent (direct link) 300 MB/s


PC to device extent (over the network) 285 MB/s
PC to device extent (direct link) 260 MB/s


Two things that I wasn't expecting, speeds over the network were faster than a direct link from the PC to the FreeNAS box.? Secondly, slightly better speeds using file rather than a device extent. Now if I've followed things correctly then the reason to create a zvol and use a device extent over a file extent is to get the benefits from ZFS's read and write caching, so where are they here?

One other thing I'm not quite clear on is how the file extent works exactly, why can't you just point it to a dataset?

 

[dlavigne]

Which version of FreeNAS?

 

[jgreco]

"Direct link" is a subset of "over the network," not a different beast. You may have some device compatibility issue or configuration issue.

Are you meaning MByte/sec or Mbit/sec? Because "320 MB/s" reads most closely as MByte/sec, which is in excess of 1Gbps ethernet.

 

[Nick Howard]

I'm on version 9.3 and it's Mbit/sec I believe. MB/s is how Windows 10 is identifying the speed. And for the direct link I'd set a different subnet up and had a cable direct from my Freenas box to the PC's 2nd nic.

 

[Nick Howard]

Also, I'm not sure if it's a bug but I can only seem to connect when using the "ALL" option on the initiator setup. I've tried various hostnames and none of them can connect.

 

[jgreco]

Try CIDR.

 

[Nick Howard]

Try CIDR.

I tried that too, also doesn't work.

 

[jgreco]

Any errors in the log?

 

[Nick Howard]

No nothing there.

 

[jgreco]

Definitely post a bug report.

 

[Nick Howard]

Will do.