On Mon, Jan 30, 2017 at 02:56:48PM +0000, Ehrenwald, Ian wrote:
It's funny you mention this - I had a support case open not more than a couple weeks ago regarding the same exact thing.
It's not really in my budget at the moment to purchase four more DS2246 with 24 x 1.2t each (2 for primary, 2 for DR) so this has rekindled my interest in trying this global throttle flag on a weekend were if IO bogs down nobody will complain (too much) :)
We saw absolutely no impact on performance on the source filers. I am sure its possible it could impact performance.
In fact I would argue our performance may have improved, because the snapmirrors now finish in just a few hours overnight when we are under light load, rather than having 20 snapmirrors running during the day for days on end.
Also, I already have a mechanism to control throttling. Each snapmirror has a throttle setting. Whats the point if the global limit makes my per mirror limit useless?
Also, data protection can be more important than performance. That should be up to us to decide, not netapp.
The bottom line is that a global snapmirror rate throttle is a great idea. It should be documented and easily controllable by the administrator and should have a reasonable default value. It appears the current throttle has none of these things.
Regards, pdg