[sheepdog-users] Running instances and snapshots

Liu Yuan namei.unix at gmail.com
Fri Jul 5 15:50:43 CEST 2013

On Fri, Jul 05, 2013 at 01:39:39PM +0000, Andrew J. Hobbs wrote:
> Perhaps I'm missing something, but if I try to use:
> qemu-img snapshot -c test someimg
> My image then goes into read-only mode.  Is there a way to snapshot a running image without entering into this read-only mode?

> Current configuration:
> 3 sheepdog nodes running 0.6.0_71_g7ccce0d, 2 are running 1.4.0 (Debian 1.4.0+dfsg-1expubuntu4), one is running a self-compiled 1.5.1.

qemu-img live snapshot is only supported by 1.5 or later.

Please try "collie vdi snapshot -s tag your_vdi", this should work.

> I have two running instances on the nodes, one with qcow2 image, the other with a raw image in sheepdog.
> My interest lies in uptime for the webserver instances.  I can cheerfully migrate the instance among the machines without issue, the next part would be being able to snapshot backup the instances without outage.
> /usr/sbin/sheep -c zookeeper:,, -j dir=/var/lib/sheepjournal,size=1024 -w size=60000,dir=/var/lib/sheepcache -y /var/lib/sheepdog
> /var/lib/sheepjournal is on a SSD OS boot drive.  /var/lib/sheepcache is on an SSD partition.  /var/lib/sheepdog is a 1 TB drive.  Using zookeeper as nodes are in different buildings, and multicast is not enabled on our switches.

Since you are using ssd, I'd suggest '-D' to enable directio for backend storage
-w directio to enable directio IO for cache. With directio enabled, sheep won't
cache single byte of IO operations in memory thus leave the memory as much as
possible for guest use.

By the way, what is performance number in your setup?


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