svn commit: r200282 - head/sbin/geom/class/mirror

[Alexander Motin]

Author: mav
Date: Tue Dec  8 22:43:29 2009
New Revision: 200282
URL: http://svn.freebsd.org/changeset/base/200282

Log:
  Change gmirror default balance algorithm from "split" to "load".
  "split" is very ineffective for devices with rotating media as HDDs.
  To be effective, it needs that transfer time reduction due to block
  splitting was bigger then access time increase due to non-sequential
  access. For modern HDDs I was able to reproduce it only with read sizes
  of 2MB and above, which is almost not applicable in real life.
  "load" algorithm same time is more universal and effective now.
  
  Reviewed by:	pjd

Modified:
  head/sbin/geom/class/mirror/geom_mirror.c

Modified: head/sbin/geom/class/mirror/geom_mirror.c
==============================================================================
--- head/sbin/geom/class/mirror/geom_mirror.c	Tue Dec  8 22:41:37 2009	(r200281)
+++ head/sbin/geom/class/mirror/geom_mirror.c	Tue Dec  8 22:43:29 2009	(r200282)
@@ -44,7 +44,7 @@ __FBSDID("$FreeBSD$");
 uint32_t lib_version = G_LIB_VERSION;
 uint32_t version = G_MIRROR_VERSION;
 
-static char label_balance[] = "split", configure_balance[] = "none";
+static char label_balance[] = "load", configure_balance[] = "none";
 static intmax_t label_slice = 4096, configure_slice = -1;
 static intmax_t insert_priority = 0, configure_priority = -1;