# HG changeset patch
# User Shriram Rajagopalan <rshriram@xxxxxxxxx>
# Date 1305604364 25200
# Node ID 666dd2576bc41ccb9f4cb74c54bd16a6425e7b14
# Parent 5fe52d24d88f3beea273d48c18d9e5ac8858ccac
remus: support DRBD disk backends
DRBD disk backends can be used instead of tapdisk backends for Remus.
This requires a Remus style disk replication protocol (asynchronous
replication with output buffering at backup), that is not available in
standard DRBD code. A modified version that supports this new replication
protocol is available from git://aramis.nss.cs.ubc.ca/drbd-8.3-remus
Use of DRBD disk backends provides a means for efficient resynchronization
of data after the crashed machine comes back online. Since DRBD allows for
online resynchronization, a DRBD backed Remus VM does not have to be stopped
or shutdown while the disks are resynchronizing. Once resynchronization is
complete,
Remus can be started at will.
Signed-off-by: Shriram Rajagopalan <rshriram@xxxxxxxxx>
diff -r 5fe52d24d88f -r 666dd2576bc4 tools/python/xen/remus/device.py
--- a/tools/python/xen/remus/device.py Mon May 16 20:47:04 2011 -0700
+++ b/tools/python/xen/remus/device.py Mon May 16 20:52:44 2011 -0700
@@ -2,7 +2,7 @@
#
# Coordinates with devices at suspend, resume, and commit hooks
-import os, re
+import os, re, fcntl
import netlink, qdisc, util
@@ -30,22 +30,51 @@
is paused between epochs.
"""
FIFODIR = '/var/run/tap'
+ SEND_CHECKPOINT = 20
+ WAIT_CHECKPOINT_ACK = 30
def __init__(self, disk):
# look up disk, make sure it is tap:buffer, and set up socket
# to request commits.
self.ctlfd = None
+ self.msgfd = None
+ self.is_drbd = False
+ self.ackwait = False
- if not disk.uname.startswith('tap:remus:') and not
disk.uname.startswith('tap:tapdisk:remus:'):
+ if disk.uname.startswith('tap:remus:') or
disk.uname.startswith('tap:tapdisk:remus:'):
+ fifo = re.match("tap:.*(remus.*)\|",
disk.uname).group(1).replace(':', '_')
+ absfifo = os.path.join(self.FIFODIR, fifo)
+ absmsgfifo = absfifo + '.msg'
+
+ self.installed = False
+ self.ctlfd = open(absfifo, 'w+b')
+ self.msgfd = open(absmsgfifo, 'r+b')
+ elif disk.uname.startswith('drbd:'):
+ #get the drbd device associated with this resource
+ drbdres = re.match("drbd:(.*)", disk.uname).group(1)
+ drbddev = util.runcmd("drbdadm sh-dev %s" % drbdres).rstrip()
+
+ #check for remus supported drbd installation
+ rconf = util.runcmd("drbdsetup %s show" % drbddev)
+ if rconf.find('protocol D;') == -1:
+ raise ReplicatedDiskException('Remus support for DRBD disks
requires the '
+ 'resources to operate in
protocol D. Please make '
+ 'sure that you have installed
the remus supported DRBD '
+ 'version from
git://aramis.nss.cs.ubc.ca/drbd-8.3-remus '
+ 'and enabled protocol D in the
resource config')
+
+ #check if resource is in connected state
+ cstate = util.runcmd("drbdadm cstate %s" % drbdres).rstrip()
+ if cstate != 'Connected':
+ raise ReplicatedDiskException('DRBD resource %s is not in
connected state!'
+ % drbdres)
+
+ #open a handle to the resource so that we could issue chkpt ioctls
+ self.ctlfd = open(drbddev, 'r')
+ self.is_drbd = True
+ else:
raise ReplicatedDiskException('Disk is not replicated: %s' %
str(disk))
- fifo = re.match("tap:.*(remus.*)\|", disk.uname).group(1).replace(':',
'_')
- absfifo = os.path.join(self.FIFODIR, fifo)
- absmsgfifo = absfifo + '.msg'
-
- self.installed = False
- self.ctlfd = open(absfifo, 'w+b')
- self.msgfd = open(absmsgfifo, 'r+b')
def __del__(self):
self.uninstall()
@@ -56,12 +85,24 @@
self.ctlfd = None
def postsuspend(self):
- os.write(self.ctlfd.fileno(), 'flush')
+ if not self.is_drbd:
+ os.write(self.ctlfd.fileno(), 'flush')
+ elif not self.ackwait:
+ if (fcntl.ioctl(self.ctlfd.fileno(), self.SEND_CHECKPOINT, 0) > 0):
+ self.ackwait = False
+ else:
+ self.ackwait = True
+
+ def preresume(self):
+ if self.is_drbd and self.ackwait:
+ fcntl.ioctl(self.ctlfd.fileno(), self.WAIT_CHECKPOINT_ACK, 0)
+ self.ackwait = False
def commit(self):
- msg = os.read(self.msgfd.fileno(), 4)
- if msg != 'done':
- print 'Unknown message: %s' % msg
+ if not self.is_drbd:
+ msg = os.read(self.msgfd.fileno(), 4)
+ if msg != 'done':
+ print 'Unknown message: %s' % msg
### Network
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