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

In response to Mark Mielke <mark(at)mark(dot)mielke(dot)cc>:

> 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:

From where did you draw that conclusion? Note that the "split" algorithm
(which is the default) divides requests up among multiple drives. I'm
unclear as to how you reached a conclusion opposite of what the man page
says -- did you test and find it not to work?

>
> 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(at)mielke(dot)cc>
>
>
>
>
>
>
>
>

--
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/

wmoran(at)collaborativefusion(dot)com
Phone: 412-422-3463x4023

****************************************************************
IMPORTANT: This message contains confidential information and is
intended only for the individual named. If the reader of this
message is not an intended recipient (or the individual
responsible for the delivery of this message to an intended
recipient), please be advised that any re-use, dissemination,
distribution or copying of this message is prohibited. Please
notify the sender immediately by e-mail if you have received
this e-mail by mistake and delete this e-mail from your system.
E-mail transmission cannot be guaranteed to be secure or
error-free as information could be intercepted, corrupted, lost,
destroyed, arrive late or incomplete, or contain viruses. The
sender therefore does not accept liability for any errors or
omissions in the contents of this message, which arise as a
result of e-mail transmission.
****************************************************************