Windows 10 Volume Replica vs StarWind

Question

Hi,
I know Server 10 isn't finished yet, but I am interested in the storage replica feature which I believe does synchronous synchronisation. Was just wondering if someone else had some more experience with testing this feature and could explain some of the
major differences between Microsoft's replication and StarWind replication. Do we need extra hardware for the MS way, anything special? can it be run on a 2 node cluster? if it does the same job, what reasons would we have to purchasing a third party product,
can the MS implementation be a virtual SAN and be competing against the likes to StarWind and DataCore?
I would be interested to know the technical details of the differences, and why one is better than the other.
Cheers
Steve

Answer 1

Hi,
I know Server 10 isn't finished yet, but I am interested in the storage replica feature which I believe does synchronous synchronisation. Was just wondering if someone else had some more experience with testing this feature and could explain some of the
major differences between Microsoft's replication and StarWind replication. Do we need extra hardware for the MS way, anything special? can it be run on a 2 node cluster? if it does the same job, what reasons would we have to purchasing a third party product,
can the MS implementation be a virtual SAN and be competing against the likes to StarWind and DataCore?
I would be interested to know the technical details of the differences, and why one is better than the other.
Cheers
Steve
Steve,
few disclaimers to start from...
DISCLAIMER1: I do work for StarWind Software (heck, I started the Company with one more guy years ago and still own a noticeable part of it) so while I'm doing my best to be honest you cannot believe me 100% :) Making long story short: NEVER trust anything
and double-check everything vendor says to you. At least we're publishing step-by-step guides or "cooking books" and you're welcomed to use these logs to run your experiments. There's no guarantee something did not work for us would not work for
you. And vice versa :)
DISCLAIMER2: Windows Server 10 is half-baked it's not even beta so A LOT of things don't work as expected, performance sucks badly affecting functionality (see more below), a lot of things are simply locked, MSFT is not sure will it deliver everything promised
with GA or not. So it's very premature to build your company storage strategy on what you see now. Also a lot of us are under NDA and prefer not to tell anything. I'm also under NDA so the only thing I can tell is - stay tuned, there are more interesting things
coming you're going to get in love with :)
Now Storage Replica Vs. StarWind...
1) Technical. Storage Replica is a mini-filter based logical volume synchronous replication, very similar to what SteelEye DataKeeper and maybe Double-Take do. StarWind Virtual SAN is exactly what name says - basically SAN firmware running on Windows platform
and brought one level up to run on a hypervisor host, partially as a user-land service and partially as a kernel-mode driver. Storage Replica copies data blocks coming to one volume to another volume and StarWind represents distributed high performance multi-path
LUN. I/O is "bond" to local node to avoid network transactions and TCP stack is bypassed to lower latency. So LUN only "looks" like it's iSCSI and actually it's not (something similar to SMB3 SMB Direct connection that starts life as TCP
and then turns RDMA, StarWind starts as TCP and then does DMA on a local node). With Storage Replica there's a component sitting above volume and "branching out" writes (if you know about DRBD or HAST - very similar). So "by design" Storage
Replica and Virtual SAN are TOTALLY different.
2) Positioning. Storage Replica is a Disaster Recovery software with a very high uptime (nearly zero downtime with some scenarios, see below). StarWind is a Business Continuity solution with optional DR component (async replication) so does 99.99% and 99.9999%
uptime. While it's possible to achieve SOME of the scenarios with Storage Replica (we did SoFS cluster and HA VM) it's not really a goal of it. 
3) Features. StarWind does "spoofing" so places huge amounts of a distributed write back cache (RAM-based) on every node, Storage Replica from the other side uses LOG disks (that's why SSD is preferred). StarWind is "all-active" while
SR is "active-passive" by design. So I would not expect high IOPS from SR even with GA code. StarWind does other cool things like "flash-friendly" in-line 4KB deduplication (MSFT can do only 32KB block off-line one and it does steal IOPS
from storage array as data is written twice and one extra read is required by optimization process, on heavily loaded storage you either have less IOPS or no dedupe as optimization process never kicks in...). StarWind can use RAM not only for write-back cache
(AFAIK even with W10 MSFT does not do any read-write CSV cache and cannot use non-flash as a write back cache <-- double check this) but also for in-memory with upcoming VDI accelerator project. StarWind does log-structured file system so there's no data
and only LOG and with SR LOG is re-read and decoded to put on a primary storage. Making long story short: StarWind kills random 4KB I/Os and eliminates I/O blender effect, something MSFT cannot do (LSFS is not a panacea - there are scenarios that don't work
well with it...). StarWind does offloads snapshots to cheap nodes saving primary flash for hot data, so-called "inter-node tiering", NetApp & Nimble can do that and MSFT moves hot and cold data between flash and spindle on the same node only.
Etc etc etc
So... We see SR as a very basic but very important step in the right direction. If you find that SR is "good enough" for you - use it. If not - you're welcomed to deploy third-party software. MSFT does for years leave huge holes in their product
strategy (I have an impression quite a lot of their teams are run by engineers and not by guys who were buying similar solutions for real customers) leaving a lot of space to other guys. Remember: good companies create good products and excellent companies
create INFRASTRUCTURE :) MSFT is definitely a company that allows ISVs live and grow. So we're very happy with what MSFT does in general and with Windows 10 "storage" in particular. 
Now some true value for you. We've experimented to run SR in a different set of scenarios. Some:
1) Failover file server with 2 nodes and no shared storage. Works but failover is not transparent (probably because performance sucks, I hope closer to beta no need to tune failover timeout would be required to have 100% transparent one as CA SMB3 shares
provide). Please see this blog:
Storage Replica: General-Purpose File Server with NO SHARED STORAGE!!
http://www.starwindsoftware.com/blog/?p=25
2) Scale-Out File Server with 2 nodes and no shared storage. Works but with SR "active-passive" design whole SoFS idea is a bit compromised... See:
Storage Replica: Scale-Out File Server with NO SHARED STORAGE!!
http://www.starwindsoftware.com/blog/?p=42
3) Hyper-V Cluster with HA VM and 2 nodes only, again no shared storage. ALSO WORKS. You can e-mail me or PM me and I'll give you post draft, not published yet.
4) Hyper-V Cluster with guest VM cluster. DOES NOT WORK. Probably because bugs in Windows 10 as guest VM cluster on a normal shared storage DOES NOT WORK as well. Again not published yet so e-mail me.
Hope this helped a bit :)
Good luck and happy clustering!
Anton
StarWind VSAN [Virtual SAN] clusters Hyper-V without SAS, Fibre Channel, SMB 3.0 or iSCSI, uses Ethernet to mirror internally mounted SATA disks between hosts.