Skipping and resuming analysis

This page covers what happens if you use SKIP buttons during analysis.

Klennet ZFS Recovery skip and resume diagram

Klennet ZFS Recovery analysis process diagram

The analysis has six stages and ultimately ends in the result view.

The first three stages are not skippable. Starting with Object set parameters, you can skip any stage. The analysis will proceed to the next stage, using whatever data is available. Once you reach the result view, you can click Resume analysis and return to the Object Set Parameters stage. The partially completed stages keep their progress - at each stage, the analysis is resumed rather than restarted. One exception is the Checksum verification of large files. The partially verified file has to be re-verified.

Skipping stages and resuming analysis can take a long time. You may be looking at several hours with very big (100TB+) arrays and large amounts (64GB+) of RAM. This delay happens because ZFS Recovery finishes processing whatever is in the current queue instead of discarding the queue. With enough RAM, the queue is big enough to take hours to process.

Side effects of skipping stages

Skipping each stage has side effects because part of the data is unavailable for the later stages. If there is no encryption, running the analysis to the end at once is the same as the result of several skip-resume cycles. If there is encryption, some data may be missed (see below for details).

Skipping Object set parameters

If you skip the Object set parameters stage,

  • Some or all dataset names will not be available. If you resume the analysis later and wait till the end of this stage, the dataset names will be recovered and attached to their corresponding object sets.
  • If native ZFS encryption is in use, some or all encryption keys may be unavailable. The next stage (Object set analysis) is then unable to decrypt object sets and will declare them unrecoverable. This decision is not revisited if you resume the scan. Therefore, you should not skip Object set parameters if you are recovering a pool with encrypted datasets. Or, if you do skip it, plan to restart the analysis using the autosave file.

Skipping Object set analysis

The Object set analysis stage finds files and directories and groups them by transactions. The process is ordered from the newest (most recent) files to the oldest (most far back in time) transaction. So, ZFS Recovery will not recover older files if you skip object set analysis. However, if you resume the analysis later, the remaining object sets will be processed, pulling in the older files.

Skipping Checksum verification

The Checksum verification stage reads all file data and verifies which files have good content and which are damaged. If you skip it, the quality indication for files will be unavailable.

If you are interested in a specific set of files, you can select these files in the result view and verify checksums on these specific files instead of waiting for ZFS Recovery to verify all files. If you resume the analysis, the files that were already verified are not re-verified again. However, if you skip the verification midway through some very big file, this file will have to be reprocessed. The verification progress is only stored for fully-processed files.