On 5/12/07, Gerald Timothy Quimpo <[EMAIL PROTECTED]> wrote:
On Tue, 2007-05-08 at 16:36 +0800, Orlando Andico wrote:
> On 5/8/07, Rogelio Serrano <[EMAIL PROTECTED]> wrote:
> >
> > i dont use hardware raid because it is much slower than software raid.
> > and it willingly replicates filesystem blocks with errors. since the
> > boot partition is mostly read only thats fine.
>
> Tell that to people like EMC and Veritas. They seem to have built
> entire business models around hardware RAID..
Hi Orly,
Clearly EMC and Veritas are good arguments merely by their existence and
business success.
On the other hand, I'm interested in the original point. *Does*
hardware RAID replicate filesystem blocks with errors? The answer
is probably "it depends", which is fine. All good answers start with
"it depends", but depends on what?
Which RAID types does that affect most? I don't have enough experience
or theory with RAID to know things like, if you have RAID-1, is one
of the mirrors a primary (for read/write) and the second is mostly for
replication (read/write too, but preference goes to the primary). Or
does the RAID hardware (for RAID-1, anyway) actually randomly choose
which half of the mirror to write to and then (possibly) replicate
disk errors on that written half to the other half? How about RAID-5,
can data errors due to hardware errors propagate with that?
hardware raid knows nothing about filesystems. its just protects hard
disk sectors. As far as I know. Linux software raid on the other hand
has knowledge fileystems and will not replicate logical errors.
i dont know about other hardware raid solutions besides those embedded
in chipsets and ide controllers.
since i had a bad experience with xfs on hardware raid. i have always
used ext3 and software raid ever since.
i have also used dm raid with xfs, jfs and ext3 on several desktops
and i did not encounter any problems.
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