Nick Howard
Contributor
- Joined
- May 20, 2014
- Messages
- 129
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?
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?