I’d consider 64KB reasonable. If you don’t give a block size on the dd command however, expect the copy to take a long time. From: ma qiang [mailto:maqiang1984@xxxxxxxxx]
Sent: Friday, October 15, 2010 2:18 AM
To: Jeff Sturm
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] copying or dding from a VM-template resulting in the whole system getting stuck Thanks a lot. It works much better. By the way, what is the reasonable buffer size. I have tested many based on different computers, and shows different results. On Thu, Oct 14, 2010 at 9:17 PM, Jeff Sturm <jeff.sturm@xxxxxxxxxx> wrote: This on Linux? I find copying image files with O_DIRECT is helpful. With the “dd” command, try “iflag=direct” and “oflag=direct”. Use a reasonable buffer size, like bs=64k or so, to achieve a faster copy operation. -Jeff When I create a new VM by copying or dding from a VM-template, the cp/dd operation takes almost all the memory and gets one cpu rate to almost 100%, resulting in the whole system getting stuck. anyone knows how to perform this with less cost?
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