[SATLUG] lvm2 and raid again

toddwbucy toddwbucy at grandecom.net
Mon Jan 21 22:42:46 CST 2008

I can definitely understand your predicament.  I am a grad student at
UTSA trying to be a good husband and raise 3 kids.  That said the
problem, as I see it comes when you have a hardware failure on say your
raid 0.  Well that's all fine and good if you have your raid 1 on a
separate set of drives but in your case the raid 1 will be on the same
set of drives that fails.  Yeah I know that your RAID 1 will be backed
up on the drive that didn't fail.  But what a pain the butt  this is
especially true if the drive that fails happens to be your boot drive.
Not only that but because your using the same physical drives for both
raid 0 and 1 any benefits you might have gotten from your RAid 0
partition will be defeated by your raid 1 partition.  So why bother.  If
all you have is 2 drives and you cannot afford a third then I would
either take the risk (for the speed) and go pure raid 0 and back up
every night or take the safe route and go RAID 1. 

On Mon, 2008-01-21 at 20:21 -0800, Chris Lemire wrote:
> I wish people would stop suggesting the impossible to me. I'm not going to go buy a very expensive raid controller when I haven't got the money together yet to pay a ticket. I'm a computer science college student and taking calculus 2. I don't have time to earn the money for things that everyone tells me to buy. What's in striping may fail or corrupt if I understand correctly, but my data could be backed up onto non striping partitions. I have 2 disks, and I'm not getting more any time soon.
> David Kowis <dkowis at shlrm.org> wrote: -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA512
> Chris Lemire wrote:
> > I'm not sure if I understand this correctly, but I'd like lots of people's opinions
>  on this idea. I want performance. I want to go fast. I don't to drive a
> school bus.
>  I want to drive a turbo Hayabusa. I'm thinking of reinstalling Linux
> with a different
> layout. I'm thinking it might be better to eliminate raid 0 using mdadm
> and get striping
> using lvm2. I'll put all of Linux in the lvm2 striping including / /home
> and all. Then I
>  could have a seperate partition or two dedicated for backups without
> any type of raid
>  or striping. I could make nightly backups using cron of my home
> directory while I'm
>  snoozing. I'd like to bring my computer to the install fest to set this
> up. Does anyone
>  have some thoughts? My other ideas in the past have been bad ones. I'm
> hoping this is
>  a good plan.
> Backups aren't backups unless they're on a different disk. When that
> disk fails, the entire disk is dead. All partitions.
> Also, if you want a "turbo Hayabusa" then you should go with a hardware
> raid solution. Raid0. You'd need multiple disks to make a RAID 0
> solution work. Two disks at least.
> Lvm2 will actually slow down your I/O throughput. It does however,
> provide a great deal more flexibility. Software raid is slower than
> hardware raid, because it requires software to make it happen.
> That's about the summary of things.
> - --
> David Kowis
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> -- 
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