Hi, A nice feature is ZFS is the "ZVOL" layer, that permit you to export (directly) a raw device from your zfs pool of disc, with the benefit of powerful (growing!) snapshot and easy raid management from zfs. It''s particulary usefull when you use it with virtual server, allowing you to centralize all your backup problematic, etc Does btrfs plan to support this kind of feature ? (please, don''t tell me that lvm do, lvm just sucks when you make a snapshot of your disk, and lack of the "growing", commit, rollback, diffsend feature). Thanks ! Sébastien Wacquiez PS : see http://opensolaris.org/os/community/zfs/source/zfstour.png if you don''t know what zvol do. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
zvol (interface) does not just ''export raw device'' but rather implements volume abstraction and integrates volume management into file-system. Regards, Andrey On Sun, Apr 12, 2009 at 11:26 AM, Sébastien Wacquiez <sw@enix.org> wrote:> Hi, > > A nice feature is ZFS is the "ZVOL" layer, that permit you to export > (directly) a raw device from your zfs pool of disc, with the benefit of > powerful (growing!) snapshot and easy raid management from zfs. It''s > particulary usefull when you use it with virtual server, allowing you to > centralize all your backup problematic, etc > > Does btrfs plan to support this kind of feature ? (please, don''t tell me > that lvm do, lvm just sucks when you make a snapshot of your disk, and lack > of the "growing", commit, rollback, diffsend feature). > > Thanks ! > > > Sébastien Wacquiez > > PS : see http://opensolaris.org/os/community/zfs/source/zfstour.png if you > don''t know what zvol do. > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Andrey Kuzmin a écrit :> zvol (interface) does not just ''export raw device'' but rather > implements volume abstraction and integrates volume management into > file-system. >Yep. I suck at writing english, thanks for pointing that out :) I surely mislead myself, but I think that the "volume management" of ZFS could be done with file. Alloc on write ? Use sparse file. Resizing ? Append or truncate the file. Snapshot ? Snapshot the file. Another Volume ? An other file :) In fact, the two thinks that have to be done, for me, is : 1/ Optimise the different layer to bypass permission, acl, & co, and surely the way data is written. 2/ Be able to export those file directly as block device. (Allowing some more optimisation :) ) It''s why I called this feature "export raw device" (as in "export raw file as block device"). As I say, it could be emulated with file and loopback, but it''ll surely be slow ... So I wanna know if btrfs plan to have those type of optimization (and the user land tools to simplify it''s management). Regards, Sébastien Wacquiez -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sun, Apr 12, 2009 at 10:32 PM, Sébastien Wacquiez <sw@enix.org> wrote:> Andrey Kuzmin a écrit : >> >> zvol (interface) does not just ''export raw device'' but rather >> implements volume abstraction and integrates volume management into >> file-system. >> > > Yep. I suck at writing english, thanks for pointing that out :) > > I surely mislead myself, but I think that the "volume management" of ZFS > could be done with file.Basically volume abstraction aims to provide a layer above raw device implementing extra functionality not found with raw disk (e.g., fault-tolerance), expandability (one can add disks to a volume as needed) and single point of control over a bunch of disks.> > Alloc on write ? Use sparse file. Resizing ? Append or truncate the file. > Snapshot ? Snapshot the file. Another Volume ? An other file :)Basically you''re right and, for instance, (deprecated) opensolaris user-spce iSCSI target supports exporting a regular zfs file to remote clients as raw scsi block device. At the same time, implementing a ''volume'' on-top of a regular zfs file might be unsafe (file-system makes some assumptions wrt I/O that are fine with raw devices below real volume but do not necessarily hold for a regular file) .> > In fact, the two thinks that have to be done, for me, is : > 1/ Optimise the different layer to bypass permission, acl, & co, and surely > the way data is written. > 2/ Be able to export those file directly as block device. (Allowing some > more optimisation :) ) > > It''s why I called this feature "export raw device" (as in "export raw file > as block device"). As I say, it could be emulated with file and loopback, > but it''ll surely be slow ... So I wanna know if btrfs plan to have those > type of optimization (and the user land tools to simplify it''s management). >That''s a question to linux-btrfs@, I''m quite new to this one. Regards, Andrey> > Regards, > > > Sébastien Wacquiez > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sun, 2009-04-12 at 09:26 +0200, Sébastien Wacquiez wrote:> Hi, > > A nice feature is ZFS is the "ZVOL" layer, that permit you to export > (directly) a raw device from your zfs pool of disc, with the benefit of > powerful (growing!) snapshot and easy raid management from zfs. It''s > particulary usefull when you use it with virtual server, allowing you to > centralize all your backup problematic, etc > > Does btrfs plan to support this kind of feature ? (please, don''t tell me > that lvm do, lvm just sucks when you make a snapshot of your disk, and > lack of the "growing", commit, rollback, diffsend feature). >I''ve always been interested in a btrfs export via loop or dm. The problem with loop is that it needs to be switched over to O_DIRECT or something similar. At any rate, it would be a fun project for someone looking to know dm better. -chris -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html