[libvirt] 答复: 答复: 答复: Help：Can libvirt restore several xen snapshots more faster at same time?

[Chenjia (C)]

Dear libvirt expert:
	Thanks for your replay, we are not restore from the same state file twice, only one time. we have 40 process, each process handle it's own VM and VM state file, and each process will do following things cycle: 
		While(1)
		{
			Virsh restore state file
			do something in VM in 20s
			virsh destroy vm
		}
	so we have sure now: There is currently no way to reduce these 40 xen status files space.
	
	
	When we do the above things, we got a xen crash on xen-4.7.0, so we try to use the xen-4.8.2 and libvirt 2.5.0, and the crash problem is no longer exist, but we got a new problem:
	we add the <interface> in config fie of VM:
    		<interface type='bridge'>
      			<mac address='18:c5:8a:15:c1:39'/>
      			<source bridge='virbr0'/>
   		 </interface>
	When we use 'virsh create virsh_0.xml', we can't create the vm, and got follow error:
		2017-11-28 12:36:56.329+0000: 17489: error : libxlDomainStart:1280 : internal error: libxenlight failed to create new domain 'aap_0'
			error: Failed to create domain from virsh_0.xml
			error: internal error: libxenlight failed to create new domain 'aap_0'
	and in the /var/log/libvirt/libxl/libxl-driver.log there have a log:
		2017-11-28 20:36:53 CST libxl: error: libxl_exec.c:118:libxl_report_child_exitstatus: /etc/xen/scripts/vif-bridge online [17580] exited with error status 127
		2017-11-28 20:36:53 CST libxl: error: libxl_create.c:1461:domcreate_attach_devices: unable to add nic devices.

	Could you plz help us how to process this problem? Thank you !	


-----邮件原件-----
发件人: Jim Fehlig [mailto:jfehlig at suse.com] 
发送时间: 2017年11月17日 5:58
收件人: Chenjia (C) <chenjia09 at huawei.com>; Michal Privoznik <mprivozn at redhat.com>; libvir-list at redhat.com
抄送: HUANG SHENGQIANG <huang.shengqiang at huawei.com>; Yaoshaomin <yaoshaomin at huawei.com>
主题: Re: 答复: [libvirt] 答复: Help：Can libvirt restore several xen snapshots more faster at same time?

On 11/15/2017 02:36 AM, Chenjia (C) wrote:
> Dear libvirt expert:
> 	Thanks for your reply.
> 	if  we use ' virsh restore file --bypass-cache', we got the error message: 'unsupported flags (0x1) in function libxlDomainRestoreFlags'.

--bypass-cache is not yet supported in the Xen driver. Should be easy to add, patches welcome :-).

> 	By the way , May be our goal is not  make it clear to you, add argument:'--bypass-cache'  means ' avoid file system cache when restoring', it means if we restore one state file for the second time , it will be more slower than normal , because IO is slower than cache, am I  right?

But you don't restore from the *same* file right? You restore VM1 from state- file1, VM2 from state-file2, etc., correct? Restoring from the same state file twice would result in 2 instances of the same VM. Actually, the libvirt Xen driver does not even allow this

# virsh start test-hvm
Domain test-hvm started
# virsh save test-hvm /tmp/test-save.img

Domain test-hvm saved to /tmp/test-save.img # virsh restore /tmp/test-save.img Domain restored from /tmp/test-save.img xen81:~ # virsh restore /tmp/test-save.img
error: Failed to restore domain from /tmp/test-save.img
error: Requested operation is not valid: domain 'test-hvm' is already active

Regards,
Jim