[mythtv-users] Linux software raid question
gbr at majentis.com
Thu Jun 5 12:31:32 UTC 2008
I've been running a 5x250 software raid5 array for a few years. It's easy to setup and maintain and uses very little CPU. If I had the cash, I'd prob convert to hardware raid5, and buy 2 controllers (1 spare).
Sadly, I don't have the cash, so my biggest decision now is: when I build a new system, do I go software raid 5 or software raid 6?
----- "Dan Ritter" wrote:
> On Wed, Jun 04, 2008 at 07:27:16PM -0400, Carl L. Gilbert wrote:
> > On Wed, 2008-06-04 at 15:04 -0400, Dan Ritter wrote:
> > > On Wed, Jun 04, 2008 at 02:49:11PM -0400, Carl L. Gilbert wrote:
> > > > Hardware RAID does not have to be expensive.
> > >
> > > Of course it does. Let's say that software RAID takes up 1% of
> > > your CPU. 1% of a $200 CPU is $2. There are no reliable hardware
> > > RAID systems that cost $2.
> > >
> > Your forgot to include a percentage of the cost of the drive's
> > interface. Yes, most interfaces do this today, but still. Since you
> > want to be technical, that cost is based in your motherboard.
> I don't know any general-purpose motherboards that don't have disk
> controllers these days, but let's suppose that you need to stock
> some generic SATA-PCI controllers. $10 buys a nice reliable one
> built on a Silicon Image chip.
> > > If the card blows, you had better have a replacement on hand of
> > > exactly the same type. Not so for software RAID. And if the card
> > > blows after warranty or after the manufacturer has EOL'd it, you
> > > might be looking at a very expensive replacement.
> > >
> > Hardware is hardware. If your drive controller blows it blows. Don't
> > matter if its on the MB or in a card plugged into the MB. No difference
> > here.
> Except, of course, that a RAID controller is a much more
> expensive card to keep stocked. Often more expensive than
> complete motherboards. Sometimes more expensive than complete
> motherboards, CPUs, and RAM.
> > I am not claiming HW does something software does not. You are claiming
> > the superiority of what I assume is FakeRAID.
> No, I'm claiming that superiority, in many circumstances, of
> Linux Software RAID, done through generic disk controllers and
> controlled via mdadm.
> > So what do you do when one of your drives dies on software RAID? Put in
> > a new drive and go about your business? Nope. Since you are not
> > RAIDing drives but partitions. So you have to rebuild your partition
> > table on the new drive. I don't know how thats done, but for me,
> > putting in a new drive and switching on the computer is very simple.
> # sfdisk -d /dev/good_disk |sfdisk /dev/new_disk
> > > > runs smartmon no problem. Plus there is a web interface to manage the
> > > > drives from within the OS.
> > >
> > > That's not an advantage.
> > >
> > I am claiming only 1 advantage of HW raid, Its simpler.
> I'm done trying to convince you.
> http://tao.merseine.nu/~dsr/eula.html is hereby incorporated by reference.
> When freedom gets lots of exercise, it protects itself.
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