commit b8b945187ec6a7928a05c72f064c1279a008a0c9
Author: Daniel Berteaud <daniel@firewall-services.com>
Date:   Tue May 15 23:02:28 2012 +0200

    Initial import from https://gist.github.com/1338263

diff --git a/blocksync.py b/blocksync.py
new file mode 100644
index 0000000..9235d3b
--- /dev/null
+++ b/blocksync.py
@@ -0,0 +1,154 @@
+#!/usr/bin/env python
+"""
+Synchronise block devices over the network
+
+Copyright 2006-2008 Justin Azoff <justin@bouncybouncy.net>
+Copyright 2011 Robert Coup <robert@coup.net.nz>
+License: GPL
+
+Getting started:
+
+* Copy blocksync.py to the home directory on the remote host
+* Make sure your remote user can either sudo or is root itself.
+* Make sure your local user can ssh to the remote host
+* Invoke:
+sudo python blocksync.py /dev/source user@remotehost /dev/dest
+"""
+
+import sys
+from zlib import adler32
+import subprocess
+import time
+
+SAME = "same\n"
+DIFF = "diff\n"
+
+
+def do_open(f, mode):
+    f = open(f, mode)
+    f.seek(0, 2)
+    size = f.tell()
+    f.seek(0)
+    return f, size
+
+
+def getblocks(f, blocksize):
+    while 1:
+        block = f.read(blocksize)
+        if not block:
+            break
+        yield block
+
+
+def server(dev, blocksize):
+    print dev, blocksize
+    f, size = do_open(dev, 'r+')
+    print size
+    sys.stdout.flush()
+
+    for block in getblocks(f, blocksize):
+        print "%08x" % (adler32(block) & 0xFFFFFFFF)
+        sys.stdout.flush()
+        res = sys.stdin.readline()
+        if res != SAME:
+            newblock = sys.stdin.read(blocksize)
+            f.seek(-blocksize, 1)
+            f.write(newblock)
+
+
+def sync(srcdev, dsthost, dstdev=None, blocksize=1024 * 1024):
+
+    if not dstdev:
+        dstdev = srcdev
+
+    print "Block size is %0.1f MB" % (float(blocksize) / (1024 * 1024))
+    cmd = ['ssh', '-c', 'blowfish', dsthost, 'sudo', 'python', 'blocksync.py', 'server', dstdev, '-b', str(blocksize)]
+    print "Running: %s" % " ".join(cmd)
+
+    p = subprocess.Popen(cmd, bufsize=0, stdin=subprocess.PIPE, stdout=subprocess.PIPE, close_fds=True)
+    p_in, p_out = p.stdin, p.stdout
+
+    line = p_out.readline()
+    p.poll()
+    if p.returncode is not None:
+        print "Error connecting to or invoking blocksync on the remote host!"
+        sys.exit(1)
+
+    a, b = line.split()
+    if a != dstdev:
+        print "Dest device (%s) doesn't match with the remote host (%s)!" % (dstdev, a)
+        sys.exit(1)
+    if int(b) != blocksize:
+        print "Source block size (%d) doesn't match with the remote host (%d)!" % (blocksize, int(b))
+        sys.exit(1)
+
+    try:
+        f, size = do_open(srcdev, 'r')
+    except Exception, e:
+        print "Error accessing source device! %s" % e
+        sys.exit(1)
+
+    line = p_out.readline()
+    p.poll()
+    if p.returncode is not None:
+        print "Error accessing device on remote host!"
+        sys.exit(1)
+    remote_size = int(line)
+    if size != remote_size:
+        print "Source device size (%d) doesn't match remote device size (%d)!" % (size, remote_size)
+        sys.exit(1)
+
+    same_blocks = diff_blocks = 0
+
+    print "Starting sync..."
+    t0 = time.time()
+    t_last = t0
+    for i, l_block in enumerate(getblocks(f, blocksize)):
+        l_sum = "%08x" % (adler32(l_block) & 0xFFFFFFFF)
+        r_sum = p_out.readline().strip()
+
+        if l_sum == r_sum:
+            p_in.write(SAME)
+            p_in.flush()
+            same_blocks += 1
+        else:
+            p_in.write(DIFF)
+            p_in.flush()
+            p_in.write(l_block)
+            p_in.flush()
+            diff_blocks += 1
+
+        t1 = time.time()
+        if t1 - t_last > 1:
+            rate = (i + 1.0) * blocksize / (1024.0 * 1024.0) / (t1 - t0)
+            print "\rsame: %d, diff: %d, %d/%d, %5.1f MB/s" % (same_blocks, diff_blocks, same_blocks + diff_blocks, size / blocksize, rate),
+            t_last = t1
+
+    print "\n\nCompleted in %d seconds" % (time.time() - t0)
+
+    return same_blocks, diff_blocks
+
+if __name__ == "__main__":
+    from optparse import OptionParser
+    parser = OptionParser(usage="%prog [options] /dev/source user@remotehost [/dev/dest]")
+    parser.add_option("-b", "--blocksize", dest="blocksize", action="store", type="int", help="block size (bytes)", default=1024 * 1024)
+    (options, args) = parser.parse_args()
+
+    if len(args) < 2:
+        parser.print_help()
+        print __doc__
+        sys.exit(1)
+
+    if args[0] == 'server':
+        dstdev = args[1]
+        server(dstdev, options.blocksize)
+    else:
+        srcdev = args[0]
+        dsthost = args[1]
+        if len(args) > 2:
+            dstdev = args[2]
+        else:
+            dstdev = None
+        sync(srcdev, dsthost, dstdev, options.blocksize)
+
+