K 10
svn:author
V 3
mav
K 8
svn:date
V 27
2016-12-11T19:50:39.949644Z
K 7
svn:log
V 424
Postpone ZVOL media/block size caching till first open.

At least on FreeBSD there are no legal way to access media or get its
size without opening device/provider first.  Postponing this caching
allows to skip several disk seeks per ZVOL/snapshot during import.

For HDD pool with 1 ZVOL in dev mode with 1000 snapshots this reduces
pool import time from 40 to 10 seconds.

MFC after:	2 weeks
Sponsored by:	iXsystems, Inc.

END