[SATLUG] lvm2 and raid 0

Brad Knowles brad at shub-internet.org
Mon Jan 7 15:15:51 CST 2008


It was John Pappas who left me with the impression that someone might  
mistake his statements to conclude that striping had redundancy.

I'm not saying that this is what John meant, either -- I think he was  
more focussed on the issue of how many disks are required to implement  
shat features. It's just that I felt he may have left a not-entirely- 
correct impression, which I wanted to make sure that we were all clear  
on.


There is nothing like RAID-5 that doesn't require at least three  
disks. You can do mirroring (RAID-1), but that's not really anything  
like RAID-5.


If you want to use RAID-0 for performance, I would encourage you to  
look at your actual performance baseline and see if putting / on  
RAID-0 is going to help. If your performance bottleneck is /home, then  
putting / on RAID-0 may not buy you much additional performance, while  
potentially causing a significant reduction in reliability.

You may also want to look at separating /var from everything else on /  
and putting it on a device that may have higher performance but lower  
reliability. If you were to just lose just /var instead of the entire  
root filesystem, that may be a lot less painful.

But you won't know where it makes the most sense to put what type of  
RAID configuration without looking at some sort of bottleneck analysis  
and performance baseline.

-- 
Brad Knowles <brad at shub-Internet.org>

Sent from my iPhone

On Jan 7, 2008, at 2:47 PM, Chris Lemire <good_bye300 at yahoo.com> wrote:

> I don't know why people are thinking that I said striping has  
> redundancy or raid and lvm are the same. I never said either. I know  
> raid 5 requires 3 drives. I was wondering if it is possible to have  
> something similar without 3 drivers. raid 5 offers redundancy and  
> striping. I've decided to install FC8 without LVM and use software  
> RAID only. I have 2 320 gb sata2 drives. Here's what I've decided on.
> /boot in raid 1, / in raid 0, /home in raid 1. As soon as / fails, I  
> don't lose anything important, and I can just install something  
> newer than FC8 by the time it does. And swap doesn't need to be in  
> RAID. I'll just give each swap device the same priority in the /etc/ 
> fstab for striping.
>
> Brad Knowles <brad at shub-internet.org> wrote: On 1/7/08, John Pappas  
> quoted Chris Lemire :
>
>>> Having redundancy and striping requires at least 3 hard disks,  
>>> right?
>>
>> Beyond Daniel's input,  Striping requires 2,
>
> A minor technical nit -- striping does not have any redundancy.  It
> does still require a minimum of two disks, however.
>
> -- 
> Brad Knowles
>
> LinkedIn Profile:
> -- 
> _______________________________________________
> SATLUG mailing list
> SATLUG at satlug.org
> http://alamo.satlug.org/mailman/listinfo/satlug to unsubscribe
> Powered by Rackspace (www.rackspace.com)
>
>
>
> ---------------------------------
> Be a better friend, newshound, and know-it-all with Yahoo! Mobile.   
> Try it now.
> -- 
> _______________________________________________
> SATLUG mailing list
> SATLUG at satlug.org
> http://alamo.satlug.org/mailman/listinfo/satlug to unsubscribe
> Powered by Rackspace (www.rackspace.com)


More information about the SATLUG mailing list