xdisk - Link into tree, add manual page

Operating Systems / DragonFlyBSD - Matthew Dillon [apollo.backplane.com] - 31 October 2021 02:49 UTC

- Link the xdisk driver into the tree and add a quick manual page. The xdisk driver uses libdmsg + the hammer2 service daemon to implement remote block devices over a network.

The hammer2 service daemon is the lynchpin of the system, see the section on setting up /etc/hammer2 in the hammer2 manual page for more information.

- xdisk works like a dedicated block device, so is NOT like a NFS share. At any given time, a particular block device should only be open for writing by a single client. The driver needs some work w/regards to maintaining open ref counts and such across the mini-cloud. Multiple clients should not try to share the same block device.

That said, filesystem performance over xdisk block devices should be
very good. Since the filesystem is running on the client-side, system buffer cache, read-ahead, and write buffering may be fully employed and performance will generally be better than NFS.

- Note that libdmsg has been in the tree awhile but is still considered highly experimental. It uses encrypted connections but the encryption is not considered to be robust at this time. Authentication is implemented
via a combination of public/private key pairs and IP addresses.

The hammer2 manual page describes the directives that may be used to create these keys.

28616d01bb xdisk - Link into tree, add manual page
share/man/man4/Makefile | 1 +
share/man/man4/xdisk.4 | 112 ++++++++++++++++++++++++++++++++++++++++++++++++
sys/dev/disk/Makefile | 1 +
3 files changed, 114 insertions(+)

Upstream: gitweb.dragonflybsd.org

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