VMware vSphere Review

Replication: VMware vSphere vs. Veeam Backup

VMware introduced replication in vSphere 5.5. The biggest limitation is that it only provides a single restore point only. This is an immediate show stopper for most customers. 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.

Unlike VMware replication Veeam takes advantage of multiple restore points.
For every replica, Veeam Backup & Replication creates and maintains a configurable number of restore points. If the original VM fails for any reason, you can temporary or permanently fail over to a replica and restore critical services with minimum downtime. If the latest state of a replica is not usable (for example, if corrupted data was replicated from source to target), you can select previous restore point to fail over to. Veeam Backup & Replication utilizes VMware ESX snapshot capabilities to create and manage replica restore points.

Replication of VMware VMs works similarly to forward incremental backup. During the first run of a replication job, Veeam Backup & Replication copies the original VM running on the source host and creates its full replica on the target host. You can also seed this initial copy at the target site. Unlike backup files, replica virtual disks are stored uncompressed in their native format. All subsequent replication job runs are incremental (that is, Veeam Backup & Replication copies only those data blocks that have changed since the last replication cycle).

Veeam Replication really stands out on top of the feature lacking VMware Replication. The numerous missing features like taking advantage of multiple snapshot replications, to help insure data integrity, no failback, no traffic throttling and no traffic compression etc., translate to only using VMware replication for simple use cases.

**Disclosure: My company has a business relationship with this vendor other than being a customer: I work for a VMware Partner
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author avatarit_user234723 (Senior Cloud Engineer at a comms service provider with 51-200 employees)
Top ReviewerVendor

I think the information here is rather dated (seems to be based on a 2012 thread on the Veeam forums - http://forums.veeam.com/vmware-vsphere-f24/veeam-vs-vsphere-replication-t13467.html) and quite a lot has changed in three years. The main ones are below but I imagine there are others - I didn't have time to do a thorough comparison;
1. vSphere Replication as of v5.5 can handle multiple restore points (up to 24), based on this article - http://blogs.vmware.com/vsphere/2013/09/whats-new-vr-and-srm-5-5.html
2. Application awareness is now built-in (both Windows and Linux) - http://www.vxpertise.net/2015/03/vsphere-replication-6-0-part-1-architecture-features-at-a-glance-vsphere-replication-standalone/
2. It's not quite an apples to apples comparison as vSphere Replication is included in most vSphere editions (Essentials Plus and higher) whereas Veeam Replication is an additional paid for product.

To be fair I've not really used vSphere Replication in anger (just in my lab) whereas I have used Veeam (and I'm a fan of Veeam's products and support).

author avatarit_user244245 (Vice President, Product Management with 1,001-5,000 employees)

Hi, Ed - just a few notes:
2. This is not entire correct, as there is still no application-aware logic - such as Exchange transaction logs processing - but rather, only basic VSS integration for application consistency.
3. Likewise, most users buy Veeam to meet their backup requirements - and so replication also comes "for free" there as well ;)
I do agree that a lot has changed since my post above, but Veeam was moving much faster during this time, and also added lots and lots of new functionality not currently available with vSphere Replication. From major things - replication from storage snapshots, built-in WAN acceleraction, replication from backup files to name a few - all not available with vSphere Replication. And more to come in v9 in just a few months ;)

author avatarit_user292455 (User with 51-200 employees)

Just to complete the story..
vSphere Replication also does network compression and isolation.

Also, vSphere Essentials Plus(and above) also come with a backup solution 'included', vDP Adv. based on EMC Avamar. It has many of the features you mention above, at no additional cost since March 2015
I won't go through all the features but, if you're interested, please take the time to update your information.


author avatarit_user384207 (Manager / Architect - Platform Services at a manufacturing company with 1,001-5,000 employees)

VMware's replication is quirky and buggy. With every release the product changes. We have been using it and are getting ready to move to Veeam as VMware can not get their replication stable. Currently if a volume has issues replicating under many situation you will not get any alert from vcenter and the status will show green/OK. VMware support says that is normal, status is showing last status? HUH? If it fails that is the current status and should reflect that not the last known good, what is the point. I can see why more and more people are looking to move away from VMware. They are in denial.