topic Re: How to implement "real-time" snapmirror repliaction? in Data Protection

How to implement "real-time" snapmirror repliaction?

remr1n — Wed, 04 Jun 2025 09:52:07 GMT

hey guys.

I have 2 diffrent netapp under 1 roof (AFF250 running ONTAP9.10 and FAS2650 running NTAP9.9.1). The AFF250 has a CIFS SVM thats hosting a file server of some sort and i want to create a "realtime" snapmirror replication between the AFF250 and FAS2650. I understand i have to create a new SVM and Cluster/SVM peering with the AFF250. But when it comes to actually implementing what i want to do, where can i configure it so that the snapmirror will be done almost real time?

To be more specific, when a user creates a file in AFF250/CIFS, i want the created file replicated to the FAS2650 almost immediatly.

Any advice is more than appreciated. Thanks!

Re: How to implement "real-time" snapmirror repliaction?

SuperTeam — Wed, 08 Mar 2023 09:57:31 GMT

You should probably set up a synchronous snapmirror relationship:

https://www.netapp.com/pdf.html?item=/media/17174-tr4733pdf.pdf

Re: How to implement "real-time" snapmirror repliaction?

ansley_tj — Wed, 08 Mar 2023 19:43:54 GMT

Zero RPO is supported by SnapMirror Synchronous. The basic best practices are defined in TR4733 as well as the SnapMirror documentation:

Cluster/SVM Peering: Cluster and SVM peering overview with the CLI (netapp.com)
SnapMirror Synchronous basics: SnapMirror Synchronous disaster recovery basics (netapp.com)

Peer cluster
Peer SVM
Create a custom protection policy or use the built-in "Synchronous" policy
Create SnapMirror relationship with correct protection policy (previous step).
Initialize SnapMirror relationship

Re: How to implement "real-time" snapmirror repliaction?

remr1n — Mon, 13 Mar 2023 07:31:31 GMT

hey guys, thanks for the information. i have decided to go with Synchronous Snapmirror, i have created both the cluster/svm peer and then the actual SM-S job. But it isnt syncing realtime as it says it shoud. When i click refresh, it replicated the new data but when i create a file on the source volume, it doesnt replicate it to the dest volume real time, any idea whats casuing this? i cant even edit the synchronous policy so im in need of some help lol

Re: How to implement "real-time" snapmirror repliaction?

remr1n — Mon, 13 Mar 2023 07:50:43 GMT

do they actually have to be on the same ONTAP version? the source is 9.11 and the dest is 9.9.1

Re: How to implement "real-time" snapmirror repliaction?

SuperTeam — Mon, 13 Mar 2023 08:05:55 GMT

The doc (https://www.netapp.com/pdf.html?item=/media/17174-tr4733pdf.pdf) says:

SM-S interoperability SM-S supports volume replication relationships between clusters running different ONTAP versions if the difference between those ONTAP versions is no more than two higher or lower than the ONTAP version on the cluster hosting the source volume.

Re: How to implement "real-time" snapmirror repliaction?

SuperTeam — Mon, 13 Mar 2023 08:12:46 GMT

How do you know that the new files are not replicated to the destination? what's the indication?

Re: How to implement "real-time" snapmirror repliaction?

remr1n — Mon, 13 Mar 2023 08:13:01 GMT

thank you, i have confirmed that 9.9.1 and 9.11 are compatible. ive also found another thread thats similar to mine Solved: Snapmirror Synchronous isn't synching immediately - NetApp Community

i dont need to be able to write to the destination volume but i need the data written on the source volume to show up almost immediatly on the dest volume. can i achieve this without flexcache or flexclone?

thanks

Re: How to implement "real-time" snapmirror repliaction?

remr1n — Mon, 13 Mar 2023 08:22:50 GMT

well, i had 2 window opened, 1 is the source volume CIFS window (opened via windows explorer) and the other window was the destination volume CIFS window (also opened via windows explorer).

when i create a new file on source volume, i thought if i refreshed the destination CIFS window, the created file would appear. But it didnt. I had to manually press initiate "snapmirror update" in order for the new file to appear on the dest volume.

i read on the KB below that the replication happens once every hour and if i were to go and change it, i can only do so within the time frame of 30min-2hour. It seems like im better of using A-sync snapmirror with schedule time of a minute?

SnapMirror Synchronous doesn't show changes on destination volume - NetApp Knowledge Base

Re: How to implement "real-time" snapmirror repliaction?

SuperTeam — Mon, 13 Mar 2023 09:46:58 GMT

According to documentation and my testing it's not possible to schedule the async snapmirror for every 1 minute (unless you use some external scripting mechanism I guess), the minimum is every 5 minutes.

If that suits you (every 5 minutes) then async snapmirror is probably the preferred method

Re: How to implement "real-time" snapmirror repliaction?

Sergey_Osipov — Mon, 13 Mar 2023 09:49:23 GMT

You correctly found a KB.

Depending on the policy sync or stictsync the writes are or aren't accepted on the source until they are written to the destination.

However the visibility of the data on a destination depends on the snapshot.

User reads to a SnapMirror Synchronous (SM-S) destination volume are redirected to the latest exported Snapshot for the SnapMirror Synchronous relationship.
If the SnapMirror Synchronous relationship is healthy and "InSync", writes to the source volume are still being replicated synchronously and will be available in case of a disaster recovery scenario.

Meaning that when you try to read data on a destination side you always read the picture of the last replicated snapshot, however all newer data is also being replicated to destination and can be visible only in case of disaster when the relationship is broken and writable

Re: How to implement "real-time" snapmirror repliaction?

remr1n — Mon, 13 Mar 2023 09:58:48 GMT

thank you, so in other words, unless i break the relationship the right behaviour is that ill only be able to see the latest snapshot and not the latest real data.

Re: How to implement "real-time" snapmirror repliaction?

Sergey_Osipov — Mon, 13 Mar 2023 10:01:50 GMT

Yes, that is correct.

Re: How to implement "real-time" snapmirror repliaction?

SuperTeam — Mon, 13 Mar 2023 10:04:42 GMT

either break the relationship or create a flexclone for the replicated volume and create a share for the clone

Re: How to implement "real-time" snapmirror repliaction?

ansley_tj — Mon, 13 Mar 2023 13:28:50 GMT

@remr1n You will not see the "Active File System" when you are connected to the R/O DR volume...you only see the volume based on the last "common snapshot copy". We do not provide access to the AFS via CIFS/NFS.

Rest assured, the data is replicated. SM-S is meant for DR purposes more than for data distribution / secondary use cases.

You can shorten the common snapshot copy schedule to a minimum of 30 minutes.

Re: How to implement "real-time" snapmirror repliaction?

ansley_tj — Mon, 13 Mar 2023 13:31:36 GMT

You can always do a snapmirror update to "refresh" the common snapshot copy.

Re: How to implement "real-time" snapmirror repliaction?

ansley_tj — Mon, 13 Mar 2023 13:36:35 GMT

Yes, a flexclone will be a copy of the AFS.

But you would have to recreate the flexclone to get the "latest" data every time you wanted it to be available.

Re: How to implement "real-time" snapmirror repliaction?

remr1n — Wed, 15 Mar 2023 08:15:01 GMT

hey after trying several things, i was able to create a snapmirror task that replicated every minute, i did ti by creating a schedule policy using the cron option. thought id let you know!

Re: How to implement "real-time" snapmirror repliaction?

Sergey_Osipov — Wed, 15 Mar 2023 08:51:45 GMT

https://www.netapp.com/pdf.html?item=/media/17174-tr4733pdf.pdf

p.9 Common Snapshot Copy

By default, a common Snapshot copy is created every six hours. The interval between creation of each
Snapshot copy can be modified by creating a custom schedule with a minimum interval of 30 minute and
maximum interval of 24 hours. This custom schedule is then used in a custom SM-S policy or applied to
an existing SM-S policy.

manually created cron job is applied on a policy level - not relationship and it won't give you a chance to add schedule with an interval less than 30 min

here is an example from the documentation (please bear in mind this option is available within advanced level of shell)

Cluster::*> cron create -name 3hourly_schedule -hour 01,04,07,10,13,16,19,22 -minute 03
(job schedule cron create)
Cluster::*> snapmirror policy modify -policy Sync -common-snapshot-schedule 3hourly_schedule -
vserver vs1

Re: How to implement "real-time" snapmirror repliaction?

ansley_tj — Wed, 15 Mar 2023 14:07:46 GMT

@remr1n What you can do and what is supported are currently two different things...sorry. SnapMirror async is qualified and supported with a minimum schedule of 5 minutes.

Sorry.