VM replication vs vSAN on two hosts?



  • Hosts are VMware ESXi. Options are Veeam replication or VMware vSAN.
    Both replication and vSAN would be good enough when it comes to availability (a couple of hours downtime is acceptable).

    ROBUSTNESS
    Would VM replication between two hosts with local storage be more robust than vSAN on the same two hosts?

    Robust in the sense that you can get up and running no matter what. Even if something got screwed up when you updated the hypervisor software on one of the hosts or say disc corruption or some other kind of software bug or hardware failure?

    PERFORMANCE
    Also how much of a IOPs performance loss will you experience on vSAN with only two hosts versus local SSD storage?



  • @Pete-S said in VM replication vs vSAN on two hosts?:

    Options are Veeam replication or VMware vSAN.

    Why are those the options? With two hosts Starwind is the slam dunk answer. These are both secondary options that I'd list as "niche only" cases. If you have two hosts and want any kind of replication between them, I'd say you have to defend why "not" Starwind because any other solution is even entertained.



  • @Pete-S said in VM replication vs vSAN on two hosts?:

    PERFORMANCE
    Also how much of a IOPs performance loss will you experience on vSAN with only two hosts versus local SSD storage?

    Compared to Starwind, a lot. SW does RAM cache network RAID so that you have potentially better performance with it, than without, because it provides a larger cache layer.

    Of the two you mentioned, Veeam will be more performance on day to day operations, but VMware VSAN is pretty fast.



  • @Pete-S said in VM replication vs vSAN on two hosts?:

    Would VM replication between two hosts with local storage be more robust than vSAN on the same two hosts?

    No, VSAN as a concept is far more robust than Async Replication. Basically think of it as Full Sync Rep vs Async Rep. Both are replication, one is just live and one is delayed.

    Under normal circumstances, full sync is better. It gets all data, to both places, in real time. But normally it is more costly, at least traditionally. But now that the best tech out there is free (Starwind VSAN which is designed for two nodes, as opposed to Vmware VSAN which requires three nodes) there is little reason to ever entertain Async options unless there is a niche need where Full Sync simply can't be used.



  • @Pete-S said in VM replication vs vSAN on two hosts?:

    Robust in the sense that you can get up and running no matter what. Even if something got screwed up when you updated the hypervisor software on one of the hosts or say disc corruption or some other kind of software bug or hardware failure?

    Both are very robust. All costs being equal, I would do it in this order...

    1. Starwind VSAN (Full Sync, Designed for Two Nodes)
    2. VMware VSAN (Full Sync, Designed for Three Nodes)
    3. Veeam Replication (Async, Designed for Two Nodes)

    1 & 2 provide instant, automated failover which, while not required, is a huge benefit. If it costs you anything to be down, even if just the cost of you having to deal with the outage personally, then 1&2 are slam dunks and #3 should be off of the table.



  • Also worth noting, Starwind is free (and you can buy support), while 2&3 are not free. And while the cost might be included in something else, it still locks you in to those solutions unnecessarily and into those license levels. It reduces flexibility.

    And, SW is platform agnostic so you aren't locked into even the vendors in question, let alone the products and licenses. Whereas both of the others require that you use specific products and vendors for specific pieces of the puzzle.

    So while all three are good solutions, two have a lot of "cons" and not as many "pros" as the other.



  • @scottalanmiller said in VM replication vs vSAN on two hosts?:

    Also worth noting, Starwind is free (and you can buy support), while 2&3 are not free. And while the cost might be included in something else, it still locks you in to those solutions unnecessarily and into those license levels. It reduces flexibility.

    And, SW is platform agnostic so you aren't locked into even the vendors in question, let alone the products and licenses. Whereas both of the others require that you use specific products and vendors for specific pieces of the puzzle.

    So while all three are good solutions, two have a lot of "cons" and not as many "pros" as the other.

    Starwind is not an option in this case (non-technical reasons). It's VMware vSAN or replication. Veeam will be installed in any case.



  • @Pete-S I assume this is for an existing environment and that you're working to improve on the system that is in place.

    VM Replication can be made to be fully automated, whereas vSAN usually is fully automated out of the box. In either case of what you're looking at, vSAN will probably cost you more to deploy than replication.



  • @Pete-S said in VM replication vs vSAN on two hosts?:

    PERFORMANCE
    Also how much of a IOPs performance loss will you experience on vSAN with only two hosts versus local SSD storage?

    All vSAN share hardware, ESXi, Starwind etc, so I'm not sure what you mean by the above.

    You'd have to provide slightly more CPU, IOPS and RAM for ESXi's vSAN as it needs to have a third party arbitrator (preferably on it's own host and not a part of the pool).

    So with vSAN, I'd say just enough to run that third system. Which, you can setup that arbitrator on your pool, but ESXi discourages it (in their documentation and when you call about it).



  • @Pete-S said in VM replication vs vSAN on two hosts?:

    Starwind is not an option in this case (non-technical reasons). It's VMware vSAN or replication. Veeam will be installed in any case.

    Then the real fix is finding the organization problem making politics take precedence over business needs.

    Given that the results are not the driving factor here but organization emotional needs, I think your real answer then comes down to "what the organization wants" which we can't answer for them.



  • @DustinB3403 said in VM replication vs vSAN on two hosts?:

    All vSAN share hardware, ESXi, Starwind etc, so I'm not sure what you mean by the above.

    VSAN requires the live node to wait for the warm node to be caught up on writes. So generally introduces a lot of storage latency.



  • @scottalanmiller said in VM replication vs vSAN on two hosts?:

    @Pete-S said in VM replication vs vSAN on two hosts?:

    Starwind is not an option in this case (non-technical reasons). It's VMware vSAN or replication. Veeam will be installed in any case.

    Then the real fix is finding the organization problem making politics take precedence over business needs.

    Given that the results are not the driving factor here but organization emotional needs, I think your real answer then comes down to "what the organization wants" which we can't answer for them.

    Of course this is true - but he's likely not in a position to force this through, so back to the questions at hand.



  • @Dashrender said in VM replication vs vSAN on two hosts?:

    @scottalanmiller said in VM replication vs vSAN on two hosts?:

    @Pete-S said in VM replication vs vSAN on two hosts?:

    Starwind is not an option in this case (non-technical reasons). It's VMware vSAN or replication. Veeam will be installed in any case.

    Then the real fix is finding the organization problem making politics take precedence over business needs.

    Given that the results are not the driving factor here but organization emotional needs, I think your real answer then comes down to "what the organization wants" which we can't answer for them.

    Of course this is true - but he's likely not in a position to force this through, so back to the questions at hand.

    I agree, which is why I pointed out the issue and then dealt with what he can do... which is find out what political answer will result in happy managers.



  • @scottalanmiller said in VM replication vs vSAN on two hosts?:

    @Pete-S said in VM replication vs vSAN on two hosts?:

    Starwind is not an option in this case (non-technical reasons). It's VMware vSAN or replication. Veeam will be installed in any case.

    Then the real fix is finding the organization problem making politics take precedence over business needs.

    Given that the results are not the driving factor here but organization emotional needs, I think your real answer then comes down to "what the organization wants" which we can't answer for them.

    It's not emotional, it's a support question. HQ says what technology and what options they support and branch get to pick from those options. Enterprise, not SMB unfortunately.



  • vSAN is added complexity, no matter what solution you are using. Replication, is just a complete copy of your VM(s) at a set point in time.

    vSAN tries to lose nothing, as the RAM, CPU and DISKS are all migrated immediately should something happen.

    Replication may occur as often as every minute, but you could still lose files or changes within that time span that were never copied to the target.

    It really depends on what the business needs, if you can be down for a few hours, does that mean losing a few hours of work? Or just the time it takes to get things back up and running so work can pick back up?



  • @Pete-S said in VM replication vs vSAN on two hosts?:

    It's not emotional, it's a support question. HQ says what technology and what options they support and branch get to pick from those options. Enterprise, not SMB unfortunately.

    Same in enterprise. Enterprise should pick to support what is best for their needs. What makes them limit to such odd selections, someone made a choice to "not entertain what is best, but only what is already chosen." That, to me, sounds like an emotional situation. Enterprises are subject to emotions just like SMBs. I've had enterprises do it and lose millions because of that exact response.



  • @DustinB3403 said in VM replication vs vSAN on two hosts?:

    Replication may occur as often as every minute, but you could still lose files or changes within that time span that were never copied to the target.

    I think Veeam limits to every 15 minutes?



  • @scottalanmiller said in VM replication vs vSAN on two hosts?:

    @DustinB3403 said in VM replication vs vSAN on two hosts?:

    Replication may occur as often as every minute, but you could still lose files or changes within that time span that were never copied to the target.

    I think Veeam limits to every 15 minutes?

    I don't know as we don't use Veeam replication. I know other solutions can go as often as every minute. But that is outside of this scope.



  • @scottalanmiller said in VM replication vs vSAN on two hosts?:

    @DustinB3403 said in VM replication vs vSAN on two hosts?:

    Replication may occur as often as every minute, but you could still lose files or changes within that time span that were never copied to the target.

    I think Veeam limits to every 15 minutes?

    Also Veeam replication is different from using the tools within ESXi which has both replication and vSAN. I believe Veeam is being used as a second level backup solution.



  • @DustinB3403 said in VM replication vs vSAN on two hosts?:

    vSAN is added complexity, no matter what solution you are using. Replication, is just a complete copy of your VM(s) at a set point in time.

    vSAN tries to lose nothing, as the RAM, CPU and DISKS are all migrated immediately should something happen.

    Replication may occur as often as every minute, but you could still lose files or changes within that time span that were never copied to the target.

    It really depends on what the business needs, if you can be down for a few hours, does that mean losing a few hours of work? Or just the time it takes to get things back up and running so work can pick back up?

    Failures are unlikely to happen but if they did happen, reverting back to the last backup would be acceptable. If the backup or replica would be a couple of hours old, that would be acceptable too.

    What is not acceptable is to not be able to get back to a working system in a couple of hours time.

    HCI is smoother than replication from a usage point but I fear that there can be failure modes that would render both hosts inoperable. Perhaps during times when you do upgrades or configuration changes.

    Two hosts with replication between them are however still two completely independent hosts. I imagine it would be almost impossible to have a failure on one host that would make the other one inoperable.

    But maybe that's incorrect and vSAN on one host would still have all the data and work regardless of what happened to the second host?



  • @Pete-S said in VM replication vs vSAN on two hosts?:

    Two hosts with replication between them are however still two completely independent hosts. I imagine it would be almost impossible to have a failure on one host that would make the other one inoperable.
    But maybe that's incorrect and vSAN on one host would still have all the data and work regardless of what happened to the second host?

    VSAN is still replication. All approaches here are replication. One is just faster and allows for automated recovery, and one does not. You can do VSAN and not have automated recovery, or even nodal awareness to replicate (see what I did there) the autonomy of the Veeam Async approach.

    The different is in how quickly replication happens and if you wait for replication to happen before moving on with other tasks or not.

    There is an inbetween solution from vendors like DRBD where they do "real time async", so it acts like Veeam in that it does not wait for the second node to ack changes before moving on, but it sends the changes to it in real time like a VSAN so in theory the two nodes are always identical, no "delay" between when one node gets something and when the second one does.

    Really, this is all one technology, just different ways to configure it. In the case of DRBD, it's literally one tech with just a knob being tuned.



  • @Pete-S said in VM replication vs vSAN on two hosts?:

    HCI is smoother than replication from a usage point but I fear that there can be failure modes that would render both hosts inoperable.

    That's theoretically true. But it's also theoretically true with the Veeam approach. It's the automated recovery, not the VSAN, that causes any additional risks. You can use VSAN in generally without that risk.



  • @Pete-S said in VM replication vs vSAN on two hosts?:

    But maybe that's incorrect and vSAN on one host would still have all the data and work regardless of what happened to the second host?

    From a VSAN perspective, yes, that's the whole idea of the technology (at least in this kind of implementation.) Pooling VMware into a single cluster is where there is more risks.



  • @scottalanmiller said in VM replication vs vSAN on two hosts?:

    @Pete-S said in VM replication vs vSAN on two hosts?:

    But maybe that's incorrect and vSAN on one host would still have all the data and work regardless of what happened to the second host?

    From a VSAN perspective, yes, that's the whole idea of the technology (at least in this kind of implementation.) Pooling VMware into a single cluster is where there is more risks.

    OK, so if I understand correctly, vSAN, the real time synchronous replicated storage isn't the problem.

    But having VMs failover and automatically recover is what could potentially cause problems?

    So it would be an option to use vSAN as shared storage but without having the HA features in play?
    And in that case basically end up having the same functionality as Veeam replication but faster?



  • @Pete-S said in VM replication vs vSAN on two hosts?:

    But having VMs failover and automatically recover is what could potentially cause problems?

    Correct. Just replicating, whether async or sync, carries extremely little risk. But this stuff, automating VM management, is when things can go haywire.



  • @Pete-S said in VM replication vs vSAN on two hosts?:

    So it would be an option to use vSAN as shared storage but without having the HA features in play?
    And in that case basically end up having the same functionality as Veeam replication but faster?

    DOn't know if VMware VSAN gives you that option. VSAN in general does. This moves from a conceptual question to an implementation question. @NetworkNerd is the right person for that question.


  • Vendor

    @Pete-S said in VM replication vs vSAN on two hosts?:

    So it would be an option to use vSAN as shared storage but without having the HA features in play?

    This is a stupid idea. If you have vSphere HA available, enable it. It doesn't cause problems.


  • Vendor

    @scottalanmiller said in VM replication vs vSAN on two hosts?:

    DOn't know if VMware VSAN gives you that option

    It does, but you will get a health alarm, as there isn't a real reason to disable it....


  • Vendor

    @scottalanmiller said in VM replication vs vSAN on two hosts?:

    Correct. Just replicating, whether async or sync, carries extremely little risk. But this stuff, automating VM management, is when things can go haywire.

    Automatic HA with ASYNCHRONOUS replication is a terrible idea at a block or VM level. This is why Veeam doesn't support it (You would have to build your own scripts, and Gostev would likely say "this is a stupid idea"), as you are potentially automating dataloss.

    Note Veeam Replication (TODAY) uses VADP. This requires snapshots and carries performance overhead. Alternatively, in the future they will support VAIO replication (which gets you down from a 15 minute RPO to a 15 second PRO). VAIO bassed replication is a resource heavy (as is any async near-realtime write split journal system).



  • @DustinB3403 said in VM replication vs vSAN on two hosts?:

    @scottalanmiller said in VM replication vs vSAN on two hosts?:

    @DustinB3403 said in VM replication vs vSAN on two hosts?:

    Replication may occur as often as every minute, but you could still lose files or changes within that time span that were never copied to the target.

    I think Veeam limits to every 15 minutes?

    I don't know as we don't use Veeam replication. I know other solutions can go as often as every minute. But that is outside of this scope.

    Some every 30 seconds.