05.10.2013 16:38, Bruce Momjian kirjoitti: > On Fri, Oct 4, 2013 at 10:42:46PM +0300, Oskari Saarenmaa wrote: >> Thanks for the offers, but it looks like ZFS doesn't actually implement >> a similar file level clone operation. See >> https://github.com/zfsonlinux/zfs/issues/405 for discussion on a feature >> request for it. >> >> ZFS does support cloning entire datasets which seem to be similar to >> btrfs subvolume snapshots and could be used to set up a new data >> directory for a new $PGDATA. This would require the original $PGDATA >> to be a dataset/subvolume of its own and quite a bit different logic >> (than just another file copy method in pg_upgrade) to initialize the new >> version's $PGDATA as a snapshot/clone of the original. The way this >> would work is that the original $PGDATA dataset/subvolume gets cloned to >> a new location after which we move the files out of the way of the new >> PG installation and run pg_upgrade in link mode. I'm not sure if >> there's a good way to integrate this into pg_upgrade or if it's just >> something that could be documented as a fast way to run pg_upgrade >> without touching original files. >> >> With btrfs tooling the sequence would be something like this: >> >> btrfs subvolume snapshot /srv/pg92 /srv/pg93 >> mv /srv/pg93/data /srv/pg93/data92 >> initdb /data/pg93/data >> pg_upgrade --link \ >> --old-datadir=/data/pg93/data92 \ >> --new-datadir=/data/pg93/data > > Does btrfs support file system snapshots? If so, shouldn't people just > take a snapshot of the old data directory before the ugprade, rather > than using cloning?
Yeah, it's possible to clone an existing subvolume, but this requires that $PGDATA is a subvolume of its own and would be a bit difficult to integrate into existing pg_upgrade scripts. The BTRFS_IOC_CLONE ioctl operates on file level and can be used to clone files anywhere in a btrfs filesystem. / Oskari -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
