+++ /dev/null
-syncer -- Fast stateful file/disk data syncer.
-
-DESCRIPTION
-
-Main purpose of this utility is fast data synchronizing between two hard
-drives: one is fast (SSD, SATA HDD), another is connected through slow
-USB interface. Task is to lower amounts of data needed to be transferred.
-
-This utility is stateful: it keeps precomputed data hashes in separate
-statefile and use it to determine if we need to update block of data.
-
- # sync from very fast SSD to slow USB connected HDD
- % ./syncer -src /dev/ada0 -dst /dev/da0 -state state.bin
- [%%%%%%]
- # all blocks were transferred to da0
-
-Now we have statefile containing cryptographic hashes of the blocks from
-source and copy of all read data in destination. Now if we run it again:
-
- % ./syncer -src /dev/ada0 -dst /dev/da0 -state state.bin
- [....%.]
- # only one block was transferred to da0
-
-Only one modified block was transferred during this session. We read all
-data from source again, compute hashes and understand what was updated
-since the last run. Statefile is updated at the end.
-
-Utility parallelize hash computations among all found CPUs. It updates
-statefile atomically (saves data in temporary file and then renames it).
-You can configure the blocksize: shorter transfers but bigger statefile
-(it is kept in memory), or larger transfer and smaller statefile. All
-writes are sequential.
-
-syncer is free software: see the file COPYING for copying conditions.
-
-INSTALLATION
-
- % go get github.com/dchest/blake2b
- % go build
- # syncer executable file should be in current directory
-
-STATEFILE FORMAT
-
- SRC_SIZE || BLK_SIZE || HASH0 || HASH1 || ...
-
-SRC_SIZE contains size of the source, when it was firstly read. BLK_SIZE
-is the blocksize used. Both is 64-bit big-endian unsigned integers. If
-either size or blocksize differs, then syncer will deny using that
-statefile as a precaution. HASHx is BLAKE2b-512 hash output, 64 bytes.