Instead of limitating the consumed bandwidth by proposiong a configuration flag (yet another one, and which default value to be set ?), I would propose to only decrease the niceness of the process itself, so that other processes would get first the I/O access. That's not perfect I assume, but that's a quick workaround limitating the frustration.
-Sylvain 2014-02-14 4:52 GMT+01:00 Wangpan <hzwang...@corp.netease.com>: > Currently nova doesn't limit the disk IO bandwidth in copy_image() > method while creating a new instance, so the other instances on this host > may be affected by this high disk IO consuming operation, and some > time-sensitive business(e.g RDS instance with heartbeat) may be switched > between master and slave. > > So can we use the `rsync --bwlimit=${bandwidth} src dst` command instead > of `cp src dst` while copy_image in create_image() of libvirt driver, the > remote image copy operation also can be limited by `rsync > --bwlimit=${bandwidth}` or `scp -l=${bandwidth}`, this parameter > ${bandwidth} can be a new configuration in nova.conf which allow cloud > admin to config it, it's default value is 0 which means no limitation, then > the instances on this host will be not affected while a new instance with > not cached image is creating. > > the example codes: > nova/virt/libvit/utils.py: > diff --git a/nova/virt/libvirt/utils.py b/nova/virt/libvirt/utils.py > index e926d3d..5d7c935 100644 > --- a/nova/virt/libvirt/utils.py > +++ b/nova/virt/libvirt/utils.py > @@ -473,7 +473,10 @@ def copy_image(src, dest, host=None): > # sparse files. I.E. holes will not be written to DEST, > # rather recreated efficiently. In addition, since > # coreutils 8.11, holes can be read efficiently too. > - execute('cp', src, dest) > + if CONF.mbps_in_copy_image > 0: > + execute('rsync', '--bwlimit=%s' % CONF.mbps_in_copy_image * > 1024, src, dest) > + else: > + execute('cp', src, dest) > else: > dest = "%s:%s" % (host, dest) > # Try rsync first as that can compress and create sparse dest > files. > @@ -484,11 +487,22 @@ def copy_image(src, dest, host=None): > # Do a relatively light weight test first, so that we > # can fall back to scp, without having run out of space > # on the destination for example. > - execute('rsync', '--sparse', '--compress', '--dry-run', src, > dest) > + if CONF.mbps_in_copy_image > 0: > + execute('rsync', '--sparse', '--compress', '--dry-run', > + '--bwlimit=%s' % CONF.mbps_in_copy_image * 1024, > src, dest) > + else: > + execute('rsync', '--sparse', '--compress', '--dry-run', > src, dest) > except processutils.ProcessExecutionError: > - execute('scp', src, dest) > + if CONF.mbps_in_copy_image > 0: > + execute('scp', '-l', '%s' % CONF.mbps_in_copy_image * > 1024 * 8, src, dest) > + else: > + execute('scp', src, dest) > else: > - execute('rsync', '--sparse', '--compress', src, dest) > + if CONF.mbps_in_copy_image > 0: > + execute('rsync', '--sparse', '--compress', > + '--bwlimit=%s' % CONF.mbps_in_copy_image * 1024, > src, dest) > + else: > + execute('rsync', '--sparse', '--compress', src, dest) > > > 2014-02-14 > ------------------------------ > Wangpan > > _______________________________________________ > OpenStack-dev mailing list > OpenStack-dev@lists.openstack.org > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev > >
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