On Tue, Feb 26, 2013 at 9:30 PM, Martin Steigerwald <mar...@lichtvoll.de> wrote: > Am Dienstag, 26. Februar 2013 schrieb Fajar A. Nugraha: >> On Tue, Feb 26, 2013 at 11:59 AM, Mike Fleetwood >> >> <mike.fleetw...@googlemail.com> wrote: >> > On 25 February 2013 23:35, Suman C <schakr...@gmail.com> wrote: >> >> Hi, >> >> >> >> I think it would be great if there is a lvm volume or zfs zvol type >> >> support in btrfs. >> > >> > Btrfs already has capabilities to add and remove block devices on the >> > fly. Data can be stripped or mirrored or both. Raid 5/6 is in >> > testing at the moment. >> > https://btrfs.wiki.kernel.org/index.php/Using_Btrfs_with_Multiple_Devic >> > es https://btrfs.wiki.kernel.org/index.php/UseCases#RAID >> > >> > Which specific features do you think btrfs is lacking? >> >> I think he's talking about zvol-like feature. >> >> In zfs, instead of creating a >> filesystem-that-is-accessible-as-a-directory, you can create a zvol >> which behaves just like any other standard block device (e.g. you can >> use it as swap, or create ext4 filesystem on top of it). But it would >> also have most of the benefits that a normal zfs filesystem has, like: >> - thin provisioning (sparse allocation, snapshot & clone) >> - compression >> - integrity check (via checksum) >> >> Typical use cases would be: >> - swap in a pure-zfs system >> - virtualization (xen, kvm, etc) >> - NAS which exports the block device using iscsi/AoE >> >> AFAIK no such feature exist in btrfs yet. > > Sounds like the RADOS block device stuff for Ceph.
Exactly. While using files + loopback device mostly works, there were problems regarding performance and data integrity. Not to mention the hassle in accessing the data if it resides on a partition inside the file (e.g. you need losetup + kpartx to access it, and you must remember to do the reverse when you're finished with it). In zfsonlinux it's very easy to do so since a zvol is treated pretty much like a disk, and whenever there's a partition inside a zvol, a coressponding device noed is also created automatically. -- Fajar -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
