[mythtv-users] Question on software RAID

Shawn Edwards sedwards at theedwards.org
Mon Jan 26 10:19:27 EST 2004


Jeff wrote:
> At 09:52 PM 1/26/2004 +1300, you wrote:
> 
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> On Mon, 26 Jan 2004, Peter Loron wrote:
>>
>> > Once I construct a software RAID-5 under Linux, is it possible to later
>> > expand the array with more disks without erasing the contents? I'm
>> > trying to plan for my Myth box...
>>
>> Nope.
>>
>> But, you could use a LVM on top of the RAID-5 set, and when you want more
>> disk added, create another RAID-5 set and add it to the LVM.
>>
>> - --
>> David Zanetti           |  (__)
>> #include <geek/unix.h>  |  ( oo    Mooooooo
>> http://hairy.geek.nz/   |  /(_O ./
> 
> 
> Why use Raid-5? Myth doesn't really need the I/O bandwidth
> you get from striping and you said its software Raid so you're
> going to up the CPU load. Instead you could just use the LVM
> to create a large volume set which is easier to extend.
> 

Because:

a) disks break and data is lost, and
b) disks are cheap*.

I just lost a bunch of data because I did just as you proposed.  I now use LVM on top of 
software RAID1.  Makes me sleep better at night.

* depends on your definition of cheap, I know.  But you can get disks today for less 
than a dollar a gigabyte, so I'd call that 'cheap'.

-- 
Shawn Edwards
sedwards at theedwards.org

On two occasions I have been asked [by members of Parliament], 'Pray,
Mr. Babbage, if you put into the machine wrong figures, will the right answers
come out?' I am not able rightly to apprehend the kind of confusion of ideas
that could provoke such a question.  -- Charles Babbage



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