[CentOS] LVM & Stripe

Ross Walker rswwalker at gmail.com
Tue Mar 9 01:43:00 UTC 2010

On Mar 8, 2010, at 7:31 PM, Christopher Chan <christopher.chan at bradbury.edu.hk 
 > wrote:

> On Tuesday, March 09, 2010 06:40 AM, Lincoln Zuljewic Silva wrote:
>> Hello list,
>> I have a question about LVM.
>> My server has five disks and I will use it to create a LVM  
>> environment.
>> I saw in the lvcreate man page that I can use the “-i” option to  
>> set
>> the number of disks that I want to stripe the lvols, but this option
>> doesn’t exists in the “lvchange” option (in case I add new  
>> disks to
>> the VG).
>> I had in mind: create 10 lvols – “lvcreate -i5 -L 10G MyVG
>> /dev/MyVG/lvol[1-10]” and in the future, add more disks and incre 
>> ate
>> the stripe value of the existing lvols.
> I would recommend md striping over lvm but then lvm is a bit more
> flexible on that score if you have disks of varying size. What are you
> using as your physical volumes?

I actually like mdraid for raid1s then striping them with LVM for  
raid10s and it has the added benefit of passing the config to the file  
system during mkfs so it sets the chunk size and stripe width  

>> Does anybody knows how to change the parameter “-i" of a lvol that
>> already exists?
> It appears to be fixed at creation time. Kinda hard to let you mess
> around with stripesize and what not after stuff has been laid out on  
> the
> platters.

Yeah, unfortunately you can't change the interleave of a LV. You need  
to keep around 20% in reserve so when you add another PV you can  
create a new LV with the new interleave and then copy or dump/restore  
from the old LV to the new, delete the old LV, and repeat for the  
other LVs in the group. Remember to start with your largest to your  
smallest LVs.



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