we have talked about similar topic in the past weeks. IMO, let sheepdog support local backup image will promote the availability effectively, the local backup image is located in the machine where vm runs, then writeback policy is adopted just like what qcow/qcow2's backup image do. the storage size issue can be solved through decrease the number of copies. benefits: 1)network traffic will be reduced, which will also make corosync work more stable. 2)even whole sheepdog cluster crashed, the local image can still provide service. tradeoffs: 1)stronge consistency is damaged for I/O is not triggered synchronously now. to solve this problem, at least we need maintain a journal for local backup image. 2)migration of vm will became much more complicated. so, maybe this is only a transitionary solution before sheepdog archive industry available standard. Yibin Shen On Sat, Oct 8, 2011 at 3:28 AM, Mark Pace <pace at jolokianetworks.com<mailto:pace at jolokianetworks.com>> wrote: On 10/7/2011 1:20 AM, MORITA Kazutaka wrote: - hide quoted text - Other than the storage size issue, the backup node would be a bottleneck if there are many VMs. The backup node requires a huge amount of disk space and bandwidth, but if we could use such machine, we wouldn't need a clustered storage system. However, on a small cluster environment with a few nodes, the backup node idea looks good. If someone sends a patch to support it, I'll accept it. Thanks, Kazutaka I'm not sure I agree. Shared storage is a single point of failure and the reason we're looking to Sheepdog is the ability to survive a shared storage outage. Pumping a shared storage box up to provide a backup location is not nearly as expensive as creating a redundant/replicated shared storage environment that is capable of serving virtual machines properly. But, that being said, your absolutely correct in that machine is going to be beefy in large environments, etc. Now, I'm not a programmer, but would happily pay for someone to write it -- if anyone is interested, please contact me. Mark Pace -- sheepdog mailing list sheepdog at lists.wpkg.org<mailto:sheepdog at lists.wpkg.org> http://lists.wpkg.org/mailman/listinfo/sheepdog ________________________________ This email (including any attachments) is confidential and may be legally privileged. If you received this email in error, please delete it immediately and do not copy it or use it for any purpose or disclose its contents to any other person. Thank you. 本电邮(包括任何附件)可能含有机密资料并受法律保护。如您不是正确的收件人，请您立即删除本邮件。请不要将本电邮进行复制并用作任何其他用途、或透露本邮件之内容。谢谢。 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.wpkg.org/pipermail/sheepdog/attachments/20111008/a7ab4bf6/attachment.html> |