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diff --git a/doc/features/bd.txt b/doc/features/bd.txt deleted file mode 100644 index c1ba006ef8c..00000000000 --- a/doc/features/bd.txt +++ /dev/null @@ -1,130 +0,0 @@ -Sections -1. Introduction -2. Advantages -3. Creating BD backend volume -4. BD volume file -5. Using BD backend gluster volume -6. Limitations -7. TODO - -1. Introduction -=============== -Block Device translator(BD xlator) represented as storage/bd_map in -volume file adds a new backend 'block' to GlusterFS. It enables -GlusterFS to export block devices as regular files to the client. -Currently BD xlator supports exporting of 'Volume Group(VG)' as -directory and Logical Volumes(LV) within that VG as regular files to the -client. - -The eventual goal of this work is to support thin provisioning, -snapshot, copy etc of VM images seamlessly in GlusterFS storage -environment - -The immediate goal of this translator is to use LVs to store -VM images and expose them as files to QEMU/KVM. Given VG is represented -as directory and its logical volumes as files. - -BD xlator uses lvm2-devel APIs for getting the list of VGs and LVs in -the system and lvm binaries (such as lvcreate, lvresize etc) to perform -the required LV operations. - -2. Advantages -============= -By exporting LVs as regular files, it becomes possible to: -* Associate each VM to a LV so that there is no file system overhead. -* Use file system commands like cp to take copy of VM images -* Create linked clones of VM by doing LV snapshot at server -side -* Implement thin provisioning by developing a qcow2 translator - -3. Creating BD backend volume -============================= -New parameter "device vg" in volume create command is used to create BD -backend gluster volumes. - -For example - $ gluster volume create my-volume device vg hostname:/my-vg - -creates gluster volume 'my-volume' with BD backend which uses the VG -'my-vg' to store data. VG 'my-vg' should exist before creating this -gluster volume. - -4. BD volume file -================= -BD backend volume file specifies which VG to export to the client. The -section in the volume file that describes BD xlator looks like this. - -volume my-volume-bd_map -type storage/bd_map -option device vg -option export volume-group -end-volume - -option device=vg specifies that it should use VG as block backend. option -export=volume-group specifies that it should export VG "volume-group" -to the client. - -5. Using BD backend gluster volume -================================== -Mount ------ - $ mount -t glusterfs hostname:/my-volume /media/bd - $ cd /media/bd - -From the mount point: --------------------- -* Creating a new file (ie LV) involves two steps - $ touch lv1 - $ truncate -s <size> lv1 - or - $ qemu-img create -f <format> gluster:/hostname/my-volume/path-to-image <size> - -* Cloning an LV - $ ln lv1 lv2 - -* Snapshotting an LV - $ ln -s lv1 lv1-ss - -* Passing it to QEMU as one of the drives - $ qemu -drive file=<mount>/<file>,if=<if-type> - -* GlusterFS is one of the supported QEMU block drivers, the URI format - is - gluster[+transport]://[server[:port]]/my-volume/image[?socket=...] - ie - $ qemu -drive file=gluster:/hostname/my-volume/path-to-image,if=<if-type> - -Using Gluster CLI: ------------------ -* To create a new image of required size - $ gluster bd create my-volume:/path-to-image <size> - -* To delete an existing image - $ gluster bd delete my-volume:/path-to-image - -* To clone (full clone) an image - $ gluster bd clone my-volume:/path-to-image new-image - -* To take a snapshot of an image - $ gluster bd snapshot my-volume:/path-to-image snapshot-image <size> - -All gluster BD commands need size to specified in terms of KB, MB, etc. - -6. Limitations -============== -* No support to create multiple bricks -* Image creation should be used with truncate to get proper size or use - qemu-img create -* cp command can't be used to copy images, instead use ln command or - gluster bd clone command -* ln -s command throws an error even if snapshot is successful -* When ln command used on BD volumes, target file's inode is different - from target's -* Creation/deletion of directories, xattr operations, mknod and readlink - operations are not supported. - -7. TODO -======= -Add support for exporting LUNs also as a regular files. -Add support for xattr and multi brick support -Include support for device mapper thin targets |