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4 .\" by Matthew Dillon <dillon@backplane.com>
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38 .Nd Remote disk block device dmsg service
40 To compile this driver into the kernel,
41 place the following line in your
42 kernel configuration file:
43 .Bd -ragged -offset indent
47 Alternatively, to load the driver as a
48 module at boot time, place the following line in
50 .Bd -literal -offset indent
56 does not compile this driver into the kernel by default.
58 Since the userland hammer2 service daemon must be running, you cannot use
59 xdisk block devices as boot devices.
63 driver exports local block devices and imports remote block devices.
64 The devices show up under
70 It is recommended that all drive references go via
77 paths can change at a whim depending on the order of operations.
79 If a device goes away or the connection is lost, the device entry
80 remains until the ref-count drops to 0.
81 Any active I/O will hard-block.
82 Resumption of the connection resumes operations where they left off.
83 No I/O requests are lost.
84 The driver is robust across reconnection, crashes, and reboots, but
85 possibly not across power failures if the target drive loses buffered
86 write data for completed I/Os.
88 Over a 1Gbe network, synchronous D1 latency still allows for around
90 Filesystem mounts can usually max-out the line rate
91 (in excess of 100 MBytes/sec) due to filesystem read-ahead and write
96 service daemon is used as an intermediary and must be running on all
105 driver has been in the source tree a while
106 but is now automatically built and part of base as of
112 driver was written by
113 .An Matthew Dillon Aq Mt dillon@backplane.com