NetApp has offered Data ONTAP for some time in two flavours:
- Clustered Data ONTAP (cDOT)
With cDOT, NetApp has rewritten ONTAP nearly from scratch. The aim was to create an Storage OS, that leverages scale-out architecture and storage virtualization techniques, as well as providing non-disruptive operations. NetApp has needed some release cycles to get cDOT at that point, where it provides all features that customers know from 7-Mode. With Data ONTAP 8.3, NetApp has reached this point. Even Metrocluster is now supported. That’s a huge improvement and I’m glad that NetApp has made it. But NetApp wasted no time in cutting off old habits: With ONTAP 8.3, 7-Mode is no longer offered. Okay, no big deal. Customers can migrate from 7-Mode to cDOT. Yes, indeed. But it’s not that easy as you maybe think.
First of all: You can’t update to cDOT in-place. You have to wipe the nodes and re-install Data ONTAP. That makes it nearly impossible to migrate a running Filer without downtime and/ or buying or loaning additonal hardware. Most customers migrate to cDOT at the same time as they refresh the hardware. The data can be migrated on different ways. NetApp offers the 7-Mode Transition Tool (7MTT). 7MTT leverages SnapMirror to get the data from the 7-Mode to the cDOT Filer. But you can also use plain SnapMirror without 7MTT to migrate the data. The switchover from the old to the new volume is an offline process. The accessing servers have to be disconnected, and they must be connected to the new cDOT Filer and volume. 7MTT can only migrate NAS data! If you wish to migrate SAN data (LUNs), you have to use NetApps DTA2800 appliance or something like VMware Storage vMotion. Other migration techniques, like Storage vMotion, robocopy etc. can also be used.
I know that cDOT is nearly completely rewritten, but such migration paths are PITA. Especially if customers have just bought new equipment with ONTAP 8.1 or 8.2 and they now wish to migrate to 8.3.
Another pain point ist NetApps MetroCluster. With NetApp MetroCluster customers can deploy active/ active clusters between two sites up to 200 km apart. NetApp MetroCluster leverages SyncMirror to duplicate RAID groups to different disks. NetApp MetroCluster is certified for vSphere Metro Storage Cluster (vMSC). One can say that Metro cluster is a bestseller. I know many customers that use MetroCluster with only two nodes. That’s where a 2-node HA pair is cut in the middle and spread into to locations. Let’s assume that a customer is running a stretched MetroCluster with two nodes and Data ONTAP 8.2. The customer wants to migrate to ONTAP 8.3. This means, that he has to migrate to cDOT. No problem, because with ONTAP 8.3, cDOT offers support for NetApp MetroCluster.
- You can’t update to cDOT in-place. So either wipe the nodes or get (temporary) additional hardware.
- NetApp MetroCluster with cDOT requires a 2-node cluster at each of the two sites (four nodes in sum)
Especially when you look at the second statement, you will quickly realize that all customers that are running a 2-node MetroCluster, have to purchase additional nodes and disks. Otherwise they can’t use MetroCluster with cDOT. This allows only one migration path: Use ONTAP 8.2 with 7-Mode and wait until the hardware needs to be refreshed.
This is really bad… This is a shady upgrade path.
NetApp is working hard to make the migration path better.
- 7MTT is capable of migrating LUNs from 7DOT to cDOT in the newest Version
- At NetApp Insight 2014 there was an announcement of 2-Node cDOT MetroCluster which will be released soon.
Thank you Sascha for this update.
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