[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-users] copying or dding from a VM-template resulting in the whole system getting stuck
On Fri, 2010-10-15 at 10:06 -0400, Jeff Sturm wrote: > > > With the âddâ command, try âiflag=directâ and âoflag=directâ. Use a > reasonable buffer size, like bs=64k or so, to achieve a faster copy > operation. > It looks like this may depend on the particulars of the storage devices you have. For me, direct I/O was much slower, even much slower than using "cp". But using dd with a 64k buffer size was a huge speedup over "cp", thanks for the tip on that. The difference is marked enough that it will probably be worth modifying my cloning script to copy this way rather than straight cp. This is using 5GB images, a hardware raid device running RAID-5 with SCSI disks, and a DRBD-replicated file system: root@vmi1 vmgroup1]# time cp paraivm.img test.img real 0m46.174s user 0m1.324s sys 0m21.913s [root@vmi1 vmgroup1]# time dd if=paraivm.img of=test.img bs=64k 80000+0 records in 80000+0 records out 5242880000 bytes (5.2 GB) copied, 8.6259 seconds, 608 MB/s real 0m8.646s user 0m0.076s sys 0m8.505s [root@vmi1 vmgroup1]# time dd if=paraivm.img of=test.img bs=64k iflag=direct oflag=direct 80000+0 records in 80000+0 records out 5242880000 bytes (5.2 GB) copied, 109.316 seconds, 48.0 MB/s real 1m49.319s user 0m0.012s sys 0m12.209s --Greg _______________________________________________ Xen-users mailing list Xen-users@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-users
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