What you’ve heard is a bit of old news (takes time for information to get out there) Replication manager works equally with VMFS, RDMs (and very shortly) NFS datastores.

the debate on RDMs is over - they should be used very sparingly (MSCS/WSFC use cases, Oracle databases where you want to move from V to P easily to repro things, when you can’t ensure that the VMware admin won’t oversubscribe the VMFS volume on a mission-critical workload, and a few other cases - but these are rare, not the primary design point)

With “datastore” use cases - it operates very much like SMVI (and the now shipping Dell/Equallogic tool) - it uses the VI SDK to figure out what VMs are in what datastores, and the array APIs to correlate the datastore to the storage object. It then uses ESX snapshots to get a guaranteed point in time restartable image, then takes an array snapshot, then deletes all the ESX-layer snapshots.

Not sure if this can be done in the other tools, but in EMC Replication Manager, you can also select NOT to take the ESX-level snapshots.

This is important - as you get loads of VMs in a datastore, the process of doing the ESX snapshots (which are serialized per datastore) can get long. In those cases, it’s the equivalent of a “crash consistent” copy - as someone pointed out - very reliable - **but not 100% reliable**.

Lastly - it can do App-level integration for apps in VMs, on VMFS datastores, but there are some important caveats, which are covered in the docs (if you have multiple SQL server databases in one datastore - you can only do an app-integrated restore for one of them, for example).

Thanks!

Thanks for the feedback and the information on EMC’s product offerings in this area. I appreciate it!

It’s called Replication Manager. It’s supported VMware for a long time (for customers running apps in VMs), but recently added VMFS integration (for filesytem-flushed datastore level point in time copies and instant restore for datastores or VMs)

For NetApp folks - it’s equivalent to the Snap Manager family (SME, SMS, SM for Sharepoint, SMO), but is a single tool.

Dell/EqualLogic will create a similar tool at some point, as they recently started creating tools that integrate with Exchange (VSS) and SQL Server (VSS/VDI). Only NetApp and EMC have been doing this for a long time.

I’ll be doing a post on this on my blog in a bit with screenshots and a demo, as it seems to be a hot topic.

Some of us believe we should provide, within SMVI, the option to disable VMsnaps while at the same time and during initiating a NetApp snap have a Warning window pop up,cautioning the user as to the potential ramifications of such practice. Bottom line, let the user decide the value of their data and make the appropriate decision.

Others believe that even if there’s a 1% chance for FS corruption, then we ought to do whatever’s possible to avoid putting customers in this situation which means utilize VMsnaps as part of the process.

For those who are not familiar with the process SMVI follows here’s how it works:

1) Initiate NetApp snapshot request
2) SMVI call to VC over port 443 - https. VC call to lgtosync.sys driver inside the Guest. Quiesce, flush fs buffers
2) VMsnapshot
3) NetApp Snapshot
4) After NetApp snapshot completion, remove VMsnapshot

The whole process takes somewhere between 5-6 secs. Because it’s so quick, there’s barely any I/Os accumulated in the Redo Log so deleting the VMsnap is a rather quick process.

Mind you that there’s SRM integration with SMVI. The NetApp SRA (Site Recovery adapter) will leverage SMVI snapshots and create FlexClones from SMVI snapshots for site recovery testing while replication is still intact and ongoing. Furthermore, the above can occur with FC or iSCSI or a combination of both (i.e FC on Production site and iSCSI on recovery).

Cheers

Great post(s)!

I added my “2 cents” on my blog. It ended up being too much to post in a comment here.

http://vmetc.com/2008/06/07/avoid-hot-vmware-snapshots-when-using-storage-array-snapshots/#more-414

-Rich

VMFS2 had significant issues with crash consistancy, but in my experience NTFS on VMFS3 survives fairly well when you pull the plug (or recover the snapshot).

For super-critical financial applications, I am not recommending this, but three snapshots a day in this style has very rarely failed.

First, see KP’s very informative comment; in his experience, adding VMware snapshots to the mix doesn’t seem to help much. I will agree that not all workloads are good candidates for the use of VMware snapshots; this also precludes the use of most hot-backup technologies including VCB.

Second, I’d recommend application-aware utilities such as those offered by NetApp (SnapManager for Exchange, SnapManager for SQL, etc.); they can provide the guaranteed consistency and data integrity that you need for these types of applications, and their use is–as I understand it–fully supported within virtual machines.

Thanks for reading!

KP,

Thanks for your very helpful comment. Your experience in using VMware snapshots along with NetApp snapshots is very relevant. Thanks for reading!