Re: With 4 disks should I go for RAID 5 or RAID 10

[Mark Mielke <mark@xxxxxxxxxxxxxx>]

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@xxxxxxxxx>