When talking about Virtual SAN you hear a lot of people talking about the benefits, what Virtual SAN is essentially about. You see the same with various other so-called Software Defined Storage solutions. People typically, when talking about these solutions, talk about things like “enabling within 2 clicks”… Or maybe about how easy it is to scale out, or scale-up for that matter. How much performance you have because of the way they use flash drives. Or about some of the advanced data services they offer.
While all of these are important, when it comes to Virtual SAN I don’t think that is the true strength. Sure, it is great to be able to provide a well performing easy to install scale-out storage solution… but the true strength in my opinion is: Policy Based Management & Integration. After having worked with VSAN for months, that is probably what stood out the most… policy based management
What does this deep integration and what do these policies allow you to do?
- It provides the ability to specify both Performance and Availability characteristics using the UI (Web Client) or through the API.
- Number of replicas
- Stripe width
- Cache reservations
- Space reservations
- It allows you to apply policies to your workload in an easy way through the UI (or API).
- It provides the ability to do this in a granular way, per VMDK and not per datastore.
- To a group of VMs or even all VMs in a programmatic way when needed.
Over the last couple of months I have played extensively with this feature of VSAN and vCenter, and in my opinion it is by far the biggest benefit of a hypervisor-converged storage solution. Deep integration with the platform, exposed in a simplistic VM-centric way through the Web Client and/or the vSphere APIs.
Duncan,
Thank you for sharing — I totally agree. The challenge I have seen is that policy-based management is such a new concept for a lot of people that they need some help wrapping their heads around it and understanding the incredible value it can provide. Even more specifically, the *per-VM* policy-based management is a defining feature of VSAN. If something is easy to configure but doesn’t provide any additional benefit, that’s a one-time thing. The key is that policy-based management provides an ongoing benefit — something beyond the “2-clicks to enable” story.
Like most features, there need to ensure that adequate time is spent in the planning and design phase so that an implementation is successful. Often, features which are simple to enable are not given adequate design consideration: all I need to do is click this button and this checkbox! I’m sure you have seen that based on your experience with HA and DRS. =)
Even though VSAN is very flexible and allows changing of policies on the fly, I can’t stress enough the value of getting the right infrastructure in place first.
Fully agree with you on this one Doug. Infrastructure is key in this one, make sure you architect it according to your requirements.
The one policy I would love to see added would be around IOPS limits based on storage density.
For example if I have a performance policy that is defined for 2 IOPS per GB. The vmdk, based on the size, gets that IOPS limit applied to it. So if it’s a 1TB vmdk it would automagically get a 2000 IOPS limit, if it’s a 200GB vmdk it would get a 400 IOPS limit.
This would allow a service catalog to deliver storage performance options based on io density without much management complexity.
Largest storage challenge we see is noisy neighbor, if this could be contained, would be cool.
You can contain this outside of VSAN of course via the use of Storage IO Control and Storage DRS. Then there also of course is the “limit” option which you can define on a per VMDK basis.
I can understand your request though, however with VSAN it should be noted that performance is not necessarily a function of the number of GBs they have to their disposal due to the heavy use of flash.
Duncan,
Does V SAN knows how to properly manage S S D drives used for caching? I mean garbage collection, optimized writes and so on, in order to extend their life? Does it monitor and report the wear on the N AND cells so we know when is time to replace a drive?
I came here flowing through a vmware help article but I could not help myself from going through the other content. You Sir, are a genius at explaining things. And Yes, I agree completely with you on the importance of the Policy based management feature under VSAN.