[OpenIndiana-discuss] [zfs] zfs + iscsi = poor sequential reding performance

[Nikola M]

On 04/23/16 02:26 PM, Сисадмин wrote:
> for christ sake
This list is about Openindiana/illumos support so even I have some 
sympathies for proprietary VMWare/Windows users, there is just too many 
things in between that leaves many possible issues open in the chain of 
your use case and test scenario.
You can use kvm , solaris zones, VirtualBox and kvm and VBox inside 
zones on Openindiana/illumos. (and dilos has Xen on illumos)

Your conclusion about zfs+iscsi is most probably generally wrong and 
unsuited, looking at your config.
(*and I ask you not to put conclusions in the topic in the first place 
that might hurt OI and zfs)
I can suggest several things and I suggest that you use 
Openindiana/illumos on hardware and installed as an OS on machine:

First, I recently had some issues with 2 directly cable-connected OI 
machines (much lower spec) with speed not being as expected - try using 
some switch in between?
Secondly, I think that you should NOT mix hard disk types in the 
pool(512k/4K) - ashift= should be the same across the pool.
Also, you got to give your zvol volblocksize parameter bigger values 
then 4K, at least 64K and re-run, also blocksize that suits your use 
case might not be best for other use cases, so you might test what 
blocksize you mostly want and for what zvol/iscsi use. (avery zvol can 
have different blocksize, same goes for datasets with files).
And finally, try to experiment with sync=disabled for your zvols and see 
how that helps them behaving faster.

I used to use  ZFS volume for local VirtualBox use and I know that 
moving from 4K block volumes to 64 or 128K improved their speed largely 
and also with sync=disabled
and that actually, by using zvols exported via ISCSI IMPROVES disk speed 
for my VMs, then using them as just block devices serving as disk for 
VirtualBox VMs.

You are free to join on #openindiana and #illumos on Freenode etc.