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

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>