1 limitation is that it provides single restore point only. Can stop at that, this is immediate show stopper for most customers I discussed vSphere replication with. Multiple restore points are absolutely essential, because just like "good" data, any corruption/virus/dataloss from the source VM is immediately replicated to target VM, and if you don't spot the problem and perform failover to replica fast enough (before the next replication cycle) - which is going to be impossible in most cases - then you are done.
Other limitations
• No failback
• No traffic compression
• No traffic throttling
• No swap exclusion
• No network customization (network mapping)
• No re-IP upon failover
• Minimum possible RPO is 15 minutes
• Basic VSS quiescing (no application-aware processing)
• Works within single vCenter only
• No ability to create container-based jobs (explicit VM selection only)
• Limited seeding options: cannot seed from backup, or using different VM as a seed (disk IDs have to match)
• Different ports for initial and incremental sync required
• No good reporting
Also, be aware that biggest marketing push around vSphere replication is technically incorrect statement!
“Unlike other solutions, enabling vSphere replication on a VM does not impact I/O load, because it does not use VM snapshots”
It is simply impossible to transfer specific state of running VM without some sort of snapshot even in theory! In reality, during each replication cycle they do create hidden snapshot to keep the replicated state intact, just different type of snapshot (exact same concept as Veeam reversed incremental).
PROS: No commit required, snapshot is simply discarded after replication cycle completes.
CONS: While replication runs, there is 3x I/O per each modified block that belongs to the replicated state. This is the I/O impact that got lost in marketing.
I consider this to still be a better than regular snapshots for some cases, but definitely not better by a mile.
Gostev
Veeam Software
Posts: 17844
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Joined: Sun Jan 01, 2006 1:01 am
Full Name: Anton Gostev