Signed-off-by: Dan Mick <dan.mick@xxxxxxxxxxx> --- doc/README.rbd | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) create mode 100644 doc/README.rbd diff --git a/doc/README.rbd b/doc/README.rbd new file mode 100644 index 0000000..a91305a --- /dev/null +++ b/doc/README.rbd @@ -0,0 +1,26 @@ +The 'rbd' backing-store driver provides access to Ceph (http://ceph.com) +'RADOS block devices (rbd)" through tgtd. + +Ceph is a distributed storage system that provides clustered redundant +object storage; one of the ways to use such storage is through the +abstraction of a "block device". rbd devices can be mapped through a +kernel driver and show up as block devices directly, or they can be used +through userland libraries to provide backing store for things like QEMU +virtual disks. + +The bs_rbd backing-store driver allows tgtd to use rbd images as backing +storage without requiring the 'rbd' kernel block device driver, and so +avoids kernel version dependencies and the extra context switching between +kernel and userland. It also allows for userland caching of block images, +managed by librbd. + +To use bs_rbd, select --bstype rbd, and set --backing-store to an rbd +image specifier. This is of the form + + [poolname/]imagename[@snapname] + +where poolname is the RADOS pool containing the rbd image (defaults to +"rbd"), imagename is the image you want to export, and snapname is the +optional (readonly) snapshot of the image imagename. (Obviously when +a snapshot is exported, writes are not supported.) + -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe stgt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
