WIP PR for ZoL is now available : https://github.com/zfsonlinux/zfs/pull/6256
2016-07-13 13:49 GMT+02:00, Gregor Kopka <[email protected]>: > Some random though on this: > > Scrub traverses the data in the pool by digging through the metadata > structure starting from the current Uberblock (state at the current > TXG), so by definition (or my guess since I didn't dig through the code > to find out what ZFS does when the scrub reached data that got unlinked > after it was startet) it should't be able to see any new writes. > > Thus to implement functionality that depends on on-disk persistence > (pauseable scrub, storage for sorting read lists to do real scrub reads > linear in LBA order when that data wouldn't fit into RAM completely, > ...): take the handle to the last TXG as start point for scrub, then > create a dataset to use as a cache/persistance store (which will be out > of the scope of the scrub since it isn't in the metadata tree to be > examined because it'll be created on a newer TXG, if my assumption is > correct). > > Should something like this not enable persistent information (or enable > to hold all needed information through mmap'ing a volume/file as kind-of > RAM extension) about the scrub process /without/ the need of a on-disk > format change or new feature? Older systems would just see a valid > dataset ('zfs-scrub-internal-metadata' or something) so one could use a > newer ZFS to fast-scrub an old pool without the need to upgrade it (and > making it unuseable with older versions of ZFS)? > > Only downside I currently see is that this would spawn an additional > dataset in the pool that could be included in case you zfs send the > whole pool -R (or similar), or confuse the admin. > > Gregor > > > > > > ------------------------------------------- > openzfs-developer > Archives: https://www.listbox.com/member/archive/274414/=now > RSS Feed: > https://www.listbox.com/member/archive/rss/274414/28015174-0c7329d7 > Modify Your Subscription: > https://www.listbox.com/member/?member_id=28015174&id_secret=28015174-6f2fac36 > Powered by Listbox: http://www.listbox.com > ------------------------------------------ openzfs-developer Archives: https://openzfs.topicbox.com/groups/developer/discussions/T4063349fe2f43e17-Mb60624ecbe4af4971deeaf29 Powered by Topicbox: https://topicbox.com
