Data ONTAP 8 7-mode
Deduplication has a maximum flexible volume size limit. If deduplication is to be used on a volume, that volume must be within the size limit. If an attempt is made to enable deduplication on a volume that is larger than the maximum volume size, it fails with an appropriate error message. This limit varies based on the platform and Data ONTAP version. This is an important consideration when flexible volumes are moved to a different platform with a smaller maximum flexible volume size.
The deduplication maximum flexible volume size limits (including any snap reserve space) for the different NetApp storage system platforms are listed below.
- FAS2040, FAS3040, FAS3140, FAS3070, FAS3160, FAS6030, FAS6040, FAS3170, FAS3210, FAS3240, FAS3270, FAS6070, FAS6080, FAS6210, FAS6240, FAS6280: 16TB
There is a limitation on the size of the volume while enabling dedupe in FAS2050.
For FAS2050, the maximum volume size for enabling dedupe is 1TB from Data ONTAP 18.104.22.168-7.3.0, and it increased to 2TB after Data ONTAP 7.3.1 and later versions from 7.3.x. In this scenario, if you need to enable dedupe, for e.g. on a 3 TB volume, divide the 3 TB volume into 2 or more smaller volumes and then enable dedupe on it.
In Data ONTAP 8.1, volume size limitation on dedupe is removed, but FAS2050 is not supported.
For Clustered Data ONTAP, the minimum requirement is ONTAP 8.1, and, like 7-mode, there are no size limitations with this and all later versions.
Table 1 - Maximum supported volume sizes for deduplication.
Maximum Shared Data Limit For Deduplication
In addition to the maximum supported volume sizes, there is also a maximum shared data limit for deduplication. Deduplication achieves savings by keeping a single copy of a block and replacing all duplicates of that block with pointers to the single block. As a result of deduplication, much of the logical data is stored as pointers to a reduced number of physical blocks written to the volume. It is very common for a single block to have many pointer references. The logical data that ends up being stored as pointers is called shared data. The maximum shared data limit per volume for deduplication is 16TB, regardless of the platform type. Once this limit is reached, any additional new data written to the volume is not deduplicated. Writes to the volume continue to work successfully.
Maximum Total Data Limit For Deduplication
Both the maximum supported volume sizes and the maximum shared data limit for deduplication limit the maximum amount of data that can be stored within a flexible volume using deduplication. The sum of the two becomes the maximum total (logical data) size limit for a deduplicated volume.
Table 2 - Maximum total data limit in a deduplicated volume
To summarize, when using Data ONTAP 8.0.1 where the max volume sizes for all platforms is 16TB, the maximum total data limit for any storage system is:
Max Total Data Limit = [(MaxSupportedVolSize) + (MaxSharedDataLimit)]
= [ (16TB) + (16TB) ]