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Diffstat (limited to 'Documentation/admin-guide/device-mapper/writecache.rst')
-rw-r--r-- | Documentation/admin-guide/device-mapper/writecache.rst | 41 |
1 files changed, 37 insertions, 4 deletions
diff --git a/Documentation/admin-guide/device-mapper/writecache.rst b/Documentation/admin-guide/device-mapper/writecache.rst index dce0184e07ca..10429779a91a 100644 --- a/Documentation/admin-guide/device-mapper/writecache.rst +++ b/Documentation/admin-guide/device-mapper/writecache.rst @@ -12,7 +12,6 @@ first sector should contain valid superblock from previous invocation. Constructor parameters: 1. type of the cache device - "p" or "s" - - p - persistent memory - s - SSD 2. the underlying device that will be cached @@ -21,7 +20,6 @@ Constructor parameters: size) 5. the number of optional parameters (the parameters with an argument count as two) - start_sector n (default: 0) offset from the start of cache device in 512-byte sectors high_watermark n (default: 50) @@ -53,19 +51,50 @@ Constructor parameters: - some underlying devices perform better with fua, some with nofua. The user should test it + cleaner + when this option is activated (either in the constructor + arguments or by a message), the cache will not promote + new writes (however, writes to already cached blocks are + promoted, to avoid data corruption due to misordered + writes) and it will gradually writeback any cached + data. The userspace can then monitor the cleaning + process with "dmsetup status". When the number of cached + blocks drops to zero, userspace can unload the + dm-writecache target and replace it with dm-linear or + other targets. + max_age n + specifies the maximum age of a block in milliseconds. If + a block is stored in the cache for too long, it will be + written to the underlying device and cleaned up. + metadata_only + only metadata is promoted to the cache. This option + improves performance for heavier REQ_META workloads. + pause_writeback n (default: 3000) + pause writeback if there was some write I/O redirected to + the origin volume in the last n milliseconds Status: 1. error indicator - 0 if there was no error, otherwise error number 2. the number of blocks 3. the number of free blocks 4. the number of blocks under writeback +5. the number of read requests +6. the number of read requests that hit the cache +7. the number of write requests +8. the number of write requests that hit uncommitted block +9. the number of write requests that hit committed block +10. the number of write requests that bypass the cache +11. the number of write requests that are allocated in the cache +12. the number of write requests that are blocked on the freelist +13. the number of flush requests +14. the number of discard requests Messages: flush - flush the cache device. The message returns successfully + Flush the cache device. The message returns successfully if the cache device was flushed without an error flush_on_suspend - flush the cache device on next suspend. Use this message + Flush the cache device on next suspend. Use this message when you are going to remove the cache device. The proper sequence for removing the cache device is: @@ -77,3 +106,7 @@ Messages: 5. resume the device, so that it will use the linear target 6. the cache device is now inactive and it can be deleted + cleaner + See above "cleaner" constructor documentation. + clear_stats + Clear the statistics that are reported on the status line |