1.what i mean is that, when copy one lv, i would like use it's snapshot, not origin, because origin is always template. making a snapshot is very quick.
but if can take a thousand snapshots from one lv, same size as origin? while the snapshots are readable and writable?
thanks
2.nice -5 dd if=/dev/clones/from bs=64M iflag=direct |
dd of=/dev/scratch/to bs=64M oflag=direct
2.nice -5 dd if=/dev/clones/from bs=64M iflag=direct |
dd of=/dev/scratch/to bs=64M oflag=direct
the pipe base on STDIN,STDOUT. i do not think STDIN,STDOUT have too mush cache
At 2011-03-31 08:27:52，"Stuart D. Gathman" <stuart@bmsi.com> wrote: >On Wed, 30 Mar 2011, Ray Morris wrote: > >>> 1..how to pipe two copy together >> >> This is what I use after some experimenting. I've found >> it's often far faster than the more obvious use of dd: >> >> nice -5 dd if=/dev/clones/from bs=64M iflag=direct | >> dd of=/dev/scratch/to bs=64M oflag=direct >> >> I use 64 MB extents. For smaller extents, a matching dd >> block size might be good. > >Thanks for that recipe. It ought to be in lvm2 as an lvcopy utility >(dynamically determining extent size, etc). > >>> 2.i take lv as xen-guestOS's disk. usually many guestOS created >>> from one lv(called template), maybe many data is readonly, so if so >>> many lvs share readonly part ,and have its private data? COW save >>> disk space, and take less time. i do not think snapshot is sutable >>> for this case. thanks > >As long as the origin is not often modified, having many snapshots >is efficient. Each write to the origin will of course entail a write >to each snapshot. (And as I discovered recently, if write barriers are >disabled or buggy at any hardware or software layer, a power failure during >heavy writes to the origin is particularly vulnerable to write reordering >corrupting a snapshot. So make sure UPS is working before updating the >origin.) > >-- > Stuart D. Gathman <stuart@bmsi.com> > Business Management Systems Inc. Phone: 703 591-0911 Fax: 703 591-6154 >"Confutatis maledictis, flammis acribus addictis" - background song for >a Microsoft sponsored "Where do you want to go from here?" commercial. > >_______________________________________________ >linux-lvm mailing list >linux-lvm@redhat.com >https://www.redhat.com/mailman/listinfo/linux-lvm >read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
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