Re: [zfs-discuss] Snapshots and backing store
On Sep 13, 2006, at 10:52, Scott Howard wrote: It's not at all bizarre once you understand how ZFS works. I'd suggest reading through some of the documentation available at http://www.opensolaris.org/os/community/zfs/docs/ , in paricular the "Slides" available there. The presentation that 'goes' with those slides is available online: http://www.sun.com/software/solaris/zfs_learning_center.jsp ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Snapshots and backing store
Matthew Ahrens wrote: Nicolas Dorfsman wrote: Hi, There's something really bizarre in ZFS snaphot specs : "Uses no separate backing store." . Hum...if I want to mutualize one physical volume somewhere in my SAN as THE snaphots backing-store...it becomes impossible to do ! Really bad. Is there any chance to have a "backing-store-file" option in a future release ? In the same idea, it would be great to have some sort of propertie to add a disk/LUN/physical_space to a pool, only reserved to backing-store. At now, the only thing I see to disallow users to use my backing-store space for their usage is to put quota. If you want to copy your filesystems (or snapshots) to other disks, you can use 'zfs send' to send them to a different pool (which may even be on a different machine!). The confusion is probably around the word snapshot and all its various usage over the years. The one particular case people will probably slam their head into a wall is exporting snapshots to other hosts. If you can get the customer or tech to think in terms of where they want the data and how instead of snapshots, or lun copies, or whatever, it makes for an easier conversation. ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Snapshots and backing store
Nicolas Dorfsman wrote: Hi, There's something really bizarre in ZFS snaphot specs : "Uses no separate backing store." . Hum...if I want to mutualize one physical volume somewhere in my SAN as THE snaphots backing-store...it becomes impossible to do ! Really bad. Is there any chance to have a "backing-store-file" option in a future release ? In the same idea, it would be great to have some sort of propertie to add a disk/LUN/physical_space to a pool, only reserved to backing-store. At now, the only thing I see to disallow users to use my backing-store space for their usage is to put quota. If you want to copy your filesystems (or snapshots) to other disks, you can use 'zfs send' to send them to a different pool (which may even be on a different machine!). --matt ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
Re: [zfs-discuss] Snapshots and backing store
On Wed, Sep 13, 2006 at 07:38:22AM -0700, Nicolas Dorfsman wrote: > There's something really bizarre in ZFS snaphot specs : "Uses no separate > backing store." . It's not at all bizarre once you understand how ZFS works. I'd suggest reading through some of the documentation available at http://www.opensolaris.org/os/community/zfs/docs/ , in paricular the "Slides" available there. > Hum...if I want to mutualize one physical volume somewhere in my SAN as THE > snaphots backing-store...it becomes impossible to do ! Really bad. > > Is there any chance to have a "backing-store-file" option in a future > release ? Doing this would have a significant hit on performance if nothing else. Currently when you do a write to a volume which is snapshotted the system has to : 1) Write the new data (Yes, that's it - one step. OK, so I'm ignoring metadata, but...) If there was a dedicated backing store, this would change to : 1) Read the old data 2) Write the old data to the backing store 3) Write the new data 4) Free the old data (ok, so that's metadata only, but hey) ZFS isn't copy-on-write in the same way that things like ufssnap are. ufssnap is copy-on-write in that when you write something, it copies out the old data and writes it somewhere else (the backing store). ZFS doesn't need to do this - it simply writes the new data to a new location, and leaves the old data where it is. If that old data is needed for a snapshot then it's left unchanged, if it's not then it's freed. Scott ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
[zfs-discuss] Snapshots and backing store
Hi, There's something really bizarre in ZFS snaphot specs : "Uses no separate backing store." . Hum...if I want to mutualize one physical volume somewhere in my SAN as THE snaphots backing-store...it becomes impossible to do ! Really bad. Is there any chance to have a "backing-store-file" option in a future release ? In the same idea, it would be great to have some sort of propertie to add a disk/LUN/physical_space to a pool, only reserved to backing-store. At now, the only thing I see to disallow users to use my backing-store space for their usage is to put quota. Nico This message posted from opensolaris.org ___ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
