ScyllaDB Docs ScyllaDB Manual ScyllaDB for Administrators Admin Tools Nodetool Nodetool scrub

Caution

You're viewing documentation for an unstable version of ScyllaDB Manual. Switch to the latest stable version.

Nodetool scrub¶

NAME¶

scrub - Help identify and fix corrupted SSTable. Not all kinds of corruption can be skipped or fixed by scrub. Remove faulty data, eliminate tombstoned rows that have surpassed the table’s gc_grace period, and fix out-of-order rows and partitions.

SYNOPSIS¶

           nodetool [(-h <host> | --host <host>)] [(-p <port> | --port <port>)]
                [(-pp | --print-port)] [(-pw <password> | --password <password>)]
                [(-pwf <passwordFilePath> | --password-file <passwordFilePath>)]
                [(-ns | --no-snapshot)]
                [(-s | --skip-corrupted)]
                [(-m <scrub_mode> | --mode <scrub_mode>)]
                [(-q <quarantine_mode> | --quarantine-mode <quarantine_mode>)]
                [--drop-unfixable-sstables]
                [--] <keyspace> [<table...>]

Supported scrub modes: ABORT, SKIP, SEGREGATE, VALIDATE
Supported quarantine modes: INCLUDE, EXCLUDE, ONLY

OPTIONS¶

Parameter	Description
-ns / –no-snapshot	Do not take a snapshot of all scrubbed tables before starting scrub (default false).
-s / –skip-corrupted	Skip corrupted rows or partitions even when scrubbing counter tables. (Deprecated, use ‘–mode’ instead. default false)
-m <scrub_mode> / –mode <scrub_mode>	How to handle corrupt data (one of: ABORT\|SKIP\|SEGREGATE\|VALIDATE, default ABORT; overrides ‘–skip-corrupted’)
-q <quarantine_mode> / –quarantine-mode <quarantine_mode>	How to handle quarantined SSTables (one of: INCLUDE\|EXCLUDE\|ONLY, default INCLUDE)
–drop-unfixable-sstables	Drop unfixable SSTables instead of aborting the entire scrub (only valid with –mode=SEGREGATE)

-- This option can be used to separate command-line options from the list of argument, (useful when arguments might be mistaken for command-line options.

<keyspace> The keyspace to scrub.

[<table...>] Optional. One or more tables to scrub. By default, all tables in the keyspace are scrubbed.

SCRUB MODES¶

Scrub mode	Description
ABORT	Abort scrubbing when the first validation error occurs. (default).
SKIP	Skip corrupted rows or partitions. (equivalent to the legacy –skip-corrupted option). Warning: This mode can cause data loss by removing invalid data portions or entire SSTables if severely corrupted (e.g., digest mismatch detected).
SEGREGATE	Sort out-of-order rows or partitions by segregating them into additional SSTables.
VALIDATE	Read-only mode: report any corruptions found while scrubbing but do not fix them. By default, corrupt SSTables are moved into a “quarantine” subdirectory so they will not be subject to compaction.

QUARANTINE MODES¶

Quarantine mode	Description
INCLUDE	Process both regular and quarantined SSTables (default).
EXCLUDE	Process only regular (non-quarantined) SSTables.
ONLY	Process only quarantined SSTables.

Examples¶

Scrub all tables in a keyspace (mykeyspace)

> nodetool scrub mykeyspace

Scrub a specific table (mytable) in a keyspace (mykeyspace)

> nodetool scrub mykeyspace mytable

Scrub a specific table (mytable) in a keyspace (mykeyspace) in SEGREGATE mode

> nodetool scrub -m SEGREGATE mykeyspace mytable

Scrub a specific table (mytable) in a keyspace (mykeyspace) in VALIDATE mode without taking a preliminary snapshot

> nodetool scrub -m VALIDATE --no-snapshot mykeyspace mytable

Scrub a specific table (mytable) in a keyspace (mykeyspace) in SEGREGATE mode dropping unfixable SSTables

> nodetool scrub -m SEGREGATE --drop-unfixable-sstables mykeyspace mytable

Procedures for Removing Bad SSTables¶

Method 1: Quarantine and Drop¶

Step 1: Run scrub in VALIDATE mode to identify and quarantine corrupted SSTables:

> nodetool scrub -m VALIDATE keyspace_name table_name

This will move corrupted SSTables to a quarantine directory. The quarantine directory is a sub-directory of the table’s respective data directory.

Step 2 (Optional): Preserve quarantined SSTables for analysis:

Before permanently dropping the corrupted SSTables, consider copying some or all of them aside, somewhere outside of the ScyllaDB data directory, so they are preserved for later investigation by the ScyllaDB R&D team, to determine the root cause of the corruption.

# Copy quarantined SSTables to a backup location for analysis
> cp -r /path/to/data/keyspace_name/table_dir/quarantine /path/to/backup/location/

Step 3: Drop the quarantined SSTables using dropquarantinedsstables:

> nodetool dropquarantinedsstables keyspace_name table_name

This permanently removes the quarantined SSTables from the specified table.

Method 2: Segregate with Drop Unfixable Flag¶

This approach attempts to fix what can be fixed and automatically drops SSTables that cannot be fixed.

Note

This method should be used for the subset of corruption issues where SEGREGATE mode can actually help: where corruption manifests at least partly in reordered partitions or rows.

Step 1: Run scrub in SEGREGATE mode with the --drop-unfixable-sstables flag:

> nodetool scrub -m SEGREGATE --drop-unfixable-sstables keyspace_name table_name

This will:

Attempt to segregate and fix out-of-order data where possible
Remove faulty data
Automatically drop SSTables that cannot be fixed
Create new properly ordered SSTables from the recoverable data

Apache®, Apache Cassandra®, Cassandra®, the Apache feather logo and the Apache Cassandra® Eye logo are either registered trademarks or trademarks of the Apache Software Foundation in the United States and/or other countries. No endorsement by The Apache Software Foundation is implied by the use of these marks.

Was this page helpful?