Specifications

NetApp Deduplication for FAS and V-Series Deployment and Implementation Guide

OVERVIEW OF SSET

The SSET is available to NetApp system engineers, including NetApp partners, and performs nonintrusive

testing of the data set to determine the effectiveness of deduplication.

This tool is intended for use only by NetApp personnel to analyze data at current or prospective NetApp

users. By installing this software, the user agrees to keep this tool and any results from this tool confidential

between them and NetApp.

The deduplication Space Savings Estimator Tool is available for Linux

and Windows

systems, which have

the data available locally or using CIFS/NFS. See the SSET readme file for complete usage information.

LIMITATIONS OF THE SSET

The SSET runs on either a Linux system or a Windows system.

It is limited to evaluating 2TB of data or less. If the path given contains more than 2TB, once the tool has

processed the first 2TB of data, the tool indicates that the maximum size has been reached and displays the

results of the data that it has processed until that time (the rest of the data is ignored).

The tool is designed to examine data that is available either locally or using NFS/CIFS only.

For more information about SSET, read the SSET documentation. The SSET tool can be downloaded from

the NetApp internal and PartnerCenter Web sites.

3.5 DEDUPLICATION LIMITATIONS

This section discusses what’s supported and what’s not supported, and the do’s and don’ts. Some of this

information may be covered elsewhere in this report as well.

GENERAL CAVEATS

Deduplication metadata (fingerprint file and change logs) is not deduplicated.

Other metadata (such as directory metadata) is not deduplicated either. Therefore, for heavily replicated

directory environments with a large number of small files (for example, Web space), the amount of space

savings that can be achieved may be low.

Backup of the deduplicated volume using NDMP is supported, but there is no space optimization when the

data is written to tape because it’s a logical operation. (This could actually be considered an advantage,

since in this case the tape does not contain a proprietary format.)

When deduplication is used in an environment where quotas are used, the quotas cannot be oversubscribed

on a volume. For example, a user with a quota limit of 1TB can’t store more than 1TB of data in a

deduplicated volume even if this data fits into less than 1TB of physical space on the storage system.

Storage administrators can use the saved space as desired.

Only data in the active file system is deduplicated. Data pointed to by Snapshot copies that were created

before deduplication is run is not released until the Snapshot copy is deleted.

MAXIMUM FLEXIBLE VOLUME SIZE

The maximum flexible volume size limitation for deduplication varies based on the platform (this number

depends primarily on the amount of system memory). When this limit is reached, writes to the volume fail

just as they would with any other volume after it is full.

This could be important to consider if the flexible volumes are ever moved to a different platform with a

smaller maximum flexible volume size.

Table 5 shows the maximum usable flexible volume size limits (including any snap reserve space) for the

different NetApp storage system platforms. For versions of Data ONTAP prior to 7.3.1, if a volume ever gets

larger than this limit and is later shrunk to a smaller size, deduplication cannot be enabled on that volume.