[linux-lvm] Re: If one disk fails i loose everything?

[linux-lvm] Re: If one disk fails i loose everything?

[Andrew Burgess]

>Good discussion....the need to protect data under various contingencies 
>is why I use raid5 sets as the PVs.  You can lose up to two and keep 
>your data, hot add, have spares, etc.

You mean raid6

Re: [linux-lvm] Re: If one disk fails i loose everything?

[Old Fart]

Andrew Burgess wrote:
>> Good discussion....the need to protect data under various contingencies 
>> is why I use raid5 sets as the PVs.  You can lose up to two and keep 
>> your data, hot add, have spares, etc.
>>     
>
> You mean raid6
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>
>   
Actually I meant raid 5 based on actual 2 disk dropouts experienced on 
test systems and the LVM data was still available.  Probably lucky.  
Thanks for the note.

Re: [linux-lvm] Re: If one disk fails i loose everything?

[Dan Stromberg]

It really shouldn't work that way.  RAID 5 is based on XOR, and I'm
pretty sure XOR can only recover from a single-number failure.

-But-, if you had a hot spare or warm spare configured, then it would've
been possible for one drive to die, the RAID 5 to be resync'd, another
drive to die, and then still be OK.


On Tue, 2005-12-13 at 12:41 -0500, Old Fart wrote:
> Andrew Burgess wrote:
> >> Good discussion....the need to protect data under various contingencies 
> >> is why I use raid5 sets as the PVs.  You can lose up to two and keep 
> >> your data, hot add, have spares, etc.
> >>     
> >
> > You mean raid6
> >
> > _______________________________________________
> > linux-lvm mailing list
> > linux-lvm@redhat.com
> > https://www.redhat.com/mailman/listinfo/linux-lvm
> > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
> >
> >   
> Actually I meant raid 5 based on actual 2 disk dropouts experienced on 
> test systems and the LVM data was still available.  Probably lucky.  
> Thanks for the note.
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
> 

Re: [linux-lvm] Re: If one disk fails i loose everything?

[Christopher Hicks]

On Tue, 13 Dec 2005, Dan Stromberg wrote:
> It really shouldn't work that way.  RAID 5 is based on XOR, and I'm 
> pretty sure XOR can only recover from a single-number failure.
>
> -But-, if you had a hot spare or warm spare configured, then it would've 
> been possible for one drive to die, the RAID 5 to be resync'd, another 
> drive to die, and then still be OK.

Correct.  One thing to keep in mind when doing these sort of things is 
that drives from the same manufacturer and lot are more like to fail 
around the same time than random drives.  We've had two drives fail within 
a week of each other in the same raid array multiple times.  I've had a 
couple of raid arrays where it felt like I spent every other week for six 
months doing some part of a drive replacement and ending up replacing the 
whole array my the time its done.  Now if I have two drives fail in an 
array in short I proactively replace the entire thing.  Don't forget the I 
in raid means you're trying to make cheap sh*t reliable.

-- 
</chris>

The significant problems we face cannot be solved by the same level of
thinking that created them.

-- Albert Einstein