Exceeding 1TB dedupe limit

[marcconeley]

Hi People,

What happens when you exceed a volume size dedupe limit on a filer?

I have a FAS2020, with a 980Gb volume which is being used for a CIFs share and I currently have dedupe/asis running on it. And I know there is a measly 1TB dedeup limit on the FAS2020s.

What happens if I try to expand this over 1TB now? Will the vol expand but dedupe simply stop working on it, or am I going to hit a problem? e.g. not possible to expand vol, vol becomes read-only, vol has to be "un-deduped" before I can expand it over 1TB etc.

I can think of lots of bad scenarios! I am hoping dedupe just switches off and I can continue working with it as normal though!

Any ideas?

[keitha]

A small tear in the space time fabric occurs which eventually forms a black hole thus ending life as we know it...

Actually you are correct, you will no lonhger be able to dedupe the volume. Unfortunitly it means that you will no longer be able to dedupe that volume on the 2020 again (even if you delete things and shrink it back under 1TB). If you can avoid crossing that boundry do it.

Keith

[marcconeley]

A small tear in the space time fabric occurs which eventually forms a black hole thus ending life as we know it...

It's a FAS202 running 7.3.4P2 - so this could well be true!

So I am assuming whether I am running OnTap8x or my current version that the end result is the same: the vol will continue to work, but dedupe will disable itself and i'll never be able to bring it back (how about if I snapmirror the vol to another FAS? i.e. FAS 3210 which has large vol dedupe support??).

If it disables dedupe for ever more, regardless of which FAS the vol is placed on, then yes this is something I will strive to avoid (although an office network share of 1TB really isn't very big - I am forever telling my users that "yes, you may be able to buy that 5Tb disk from Tesco for €100, but it ain't an Enterprise disk").

Whereas if this is only a problem whilst the vol is located on my FAS2020, I may live with no dedupe until we upgrade the controller.

Thanks guys.

Marc

[keitha]

I'm hoping some other NetApp folks jump in because I am not 100% sure of this but from what I remember, if you Snapmirror to another larger controller you can still only dedupe the to the smaller controllers limit. However if you were to break the mirror and migrate to the larger controller you then then start to dedupe again at the larger limit however you could not reverse the replication back. It would be  one way trip... Make sense?

[marcconeley]

Yes. That makes sense.

And that would be our plan - snapmirror our data to a new filer, then break the mirror and run it from the new filer.

As long as I can re-enable dedupe when the data is on the new, more powerful filer, then I am happy.

[columbus_admin]

You haven't specified an ONTAP release, but I don't think it changed in 8.0.x

From the 7.3.2 release notes:

If volumes with deduplication exceed the maximum supported      size

In Data ONTAP 7.3.2, volumes continue to be          online when they exceed the maximum supported size. However, deduplication is          disabled on such volumes. For more information about      the maximum volume size allowed for different storage systems, with and without      deduplication, see the       Data ONTAP Storage Management Guide.       

- Scott

[keitha]

The 2020 does not support ONTAP 8 (unfortunately)

Keith

[columbus_admin]

D'oh...didn't even think about that!

- Scott