# man > cache_writeback(8)

---
type: CommandReference
command: cache_writeback
mode: man
section: 8
source: man-pages
---

## Quick Reference

- `cache_writeback --metadata-device <dev> --origin-device <dev> --fast-device <dev>` — Write back dirty blocks from the fast device to the origin device (offline recovery).

## Name

**cache_writeback** — writeback dirty blocks to the origin device.

## Synopsis

`cache_writeback` [options] `--metadata-device` {device|file} `--origin-device` {device|file} `--fast-device` {device|file}

## Description

`cache_writeback` is an offline tool that writes back dirty data to the data device (origin). Intended for use in recovery scenarios when the SSD is giving IO errors. This tool cannot be run on a live cache.

## Options

- `-h, --help` — Print help and exit.
- `-V, --version` — Print version information and exit.
- `--metadata-device {device|file}` — Location of cache metadata.
- `--origin-device {device|file}` — Slow device being cached.
- `--fast-device {device|file}` — Fast device containing the data that needs to be written back.
- `--no-metadata-update` — Do not update the metadata to clear the dirty flags. Use when decommissioning the cache.
- `--buffer-size-meg {size}` — Specify size for the metadata cache. Defaults to 16 Gig. Larger size may improve performance.
- `--list-failed-blocks` — List any blocks that failed the writeback process.

## See Also

[`cache_dump(8)`](http://localhost/phpMan.php/man/dump/8/markdown), [`cache_check(8)`](http://localhost/phpMan.php/man/check/8/markdown), [`cache_repair(8)`](http://localhost/phpMan.php/man/repair/8/markdown), [`cache_restore(8)`](http://localhost/phpMan.php/man/restore/8/markdown)