sudarshan sridhar wrote: > /Hi,/ > // > / >>Also where exactly COWed data written > / > >>>I'm not quite sure what you're asking here. Data, whether newly > written or >>>copy-on-write, goes to a newly allocated block, which > may reside on any >>>vdev, and will be spread across devices if using > RAID. > My exact doubt is, if COW is default behavior of ZFS then does COWd > data written to the same physical drive where the filesystem resides? > If so the physical device capacity should be more that what the file > system size is. > I mean in normal filesystem sinario, a partition with 1Gb with some > some filesystem (say ext2fs) is created, then use can save upto 1Gb > data under that. > Is the same behavior with ZFS?. Because I feel since COW is default > ZFS require > 1Gb for one fileystem inorder to store COWed data. > > Please correct me if i am wrong.
Unless there is a snapshot, the old blocks are freed after the new COW completes. IMHO, it is much easier to understand if you think of the vdevs as memory and the ZFS allocations as, well, memory allocations. The excellent papers on the slab allocator provide the nitty gritty details. -- richard > > -sridhar > > ------------------------------------------------------------------------ > Never miss a thing. Make Yahoo your homepage. > <http://us.rd.yahoo.com/evt=51438/*http://www.yahoo.com/r/hs> > ------------------------------------------------------------------------ > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss > _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
