Bill Moran wrote:
What do you mean "heard of"? Which raid system do you know of that reads
all drives for RAID 1?
I'm fairly sure that FreeBSD's GEOM does. Of course, it couldn't be doing
consistency checking at that point.
According to this:
http://www.freebsd.org/cgi/man.cgi?query=gmirror&apropos=0&sektion=8&manpath=FreeBSD+6-current&format=html There is a -b (balance) option that seems pretty clear that it does not read from all drives if it does not have to:
Create a mirror. The order of components is important, because a component's priority is based on its position (starting from 0). The component with the biggest priority is used by the prefer balance algorithm and is also used as a master component when resynchronization is needed, e.g. after a power failure when the device was open for writing.
Additional options include:
-b balance Specifies balance algorithm to use, one of:
load Read from the component with the lowest load.
prefer Read from the component with the biggest priority.
round-robin Use round-robin algorithm when choosing component to read.
split Split read requests, which are big- ger than or equal to slice size on N pieces, where N is the number of active components. This is the default balance algorithm.
Cheers,
mark
--
Mark Mielke <mark@mielke.cc>