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Diffstat (limited to 'Documentation/device-mapper/dm-integrity.txt')
| -rw-r--r-- | Documentation/device-mapper/dm-integrity.txt | 32 |
1 files changed, 31 insertions, 1 deletions
diff --git a/Documentation/device-mapper/dm-integrity.txt b/Documentation/device-mapper/dm-integrity.txt index 297251b0d2d5..d63d78ffeb73 100644 --- a/Documentation/device-mapper/dm-integrity.txt +++ b/Documentation/device-mapper/dm-integrity.txt @@ -21,6 +21,13 @@ mode it calculates and verifies the integrity tag internally. In this mode, the dm-integrity target can be used to detect silent data corruption on the disk or in the I/O path. +There's an alternate mode of operation where dm-integrity uses bitmap +instead of a journal. If a bit in the bitmap is 1, the corresponding +region's data and integrity tags are not synchronized - if the machine +crashes, the unsynchronized regions will be recalculated. The bitmap mode +is faster than the journal mode, because we don't have to write the data +twice, but it is also less reliable, because if data corruption happens +when the machine crashes, it may not be detected. When loading the target for the first time, the kernel driver will format the device. But it will only format the device if the superblock contains @@ -59,6 +66,10 @@ Target arguments: either both data and tag or none of them are written. The journaled mode degrades write throughput twice because the data have to be written twice. + B - bitmap mode - data and metadata are written without any + synchronization, the driver maintains a bitmap of dirty + regions where data and metadata don't match. This mode can + only be used with internal hash. R - recovery mode - in this mode, journal is not replayed, checksums are not checked and writes to the device are not allowed. This mode is useful for data recovery if the @@ -79,6 +90,10 @@ interleave_sectors:number a power of two. If the device is already formatted, the value from the superblock is used. +meta_device:device + Don't interleave the data and metadata on on device. Use a + separate device for metadata. + buffer_sectors:number The number of sectors in one buffer. The value is rounded down to a power of two. @@ -146,6 +161,15 @@ block_size:number Supported values are 512, 1024, 2048 and 4096 bytes. If not specified the default block size is 512 bytes. +sectors_per_bit:number + In the bitmap mode, this parameter specifies the number of + 512-byte sectors that corresponds to one bitmap bit. + +bitmap_flush_interval:number + The bitmap flush interval in milliseconds. The metadata buffers + are synchronized when this interval expires. + + The journal mode (D/J), buffer_sectors, journal_watermark, commit_time can be changed when reloading the target (load an inactive table and swap the tables with suspend and resume). The other arguments should not be changed @@ -167,7 +191,13 @@ The layout of the formatted block device: provides (i.e. the size of the device minus the size of all metadata and padding). The user of this target should not send bios that access data beyond the "provided data sectors" limit. - * flags - a flag is set if journal_mac is used + * flags + SB_FLAG_HAVE_JOURNAL_MAC - a flag is set if journal_mac is used + SB_FLAG_RECALCULATING - recalculating is in progress + SB_FLAG_DIRTY_BITMAP - journal area contains the bitmap of dirty + blocks + * log2(sectors per block) + * a position where recalculating finished * journal The journal is divided into sections, each section contains: * metadata area (4kiB), it contains journal entries |