[linux-lvm] why do striping and mirroring in LVM?

[Svetoslav Slavtchev]

Quoting lilha at legend.com.cn:

> 
> 
> i know that lvm support striping now and LVM2 will support mirroring
> directly later this year.
> but i'm puzzled that why lvm do that?
> 
> i think the main Goals of LVM are
>      1.Implement a very flexible virtual disk subsystem to handle disk
> storage.
>      2.Online allocation and relocation of storage.
>      3.Online extension and reduction of storage.
> And disk redundancy is the goals of  hardware. or software.RAID.
> 
> i think software.RAID+LVM is good idea,and that's enough.
it's a good idea cause LVM doesn't support mirroring and is not that good at
stripping, and it would be very good if one could use the featchers without
needing other layer ( soft RAID)
> why LVM focus on the striping and mirroring?
i think every other implementation supports them
> i don't think it's a good idea to do a big and full software.
> 
> there are any reasons and advantages to use striping or mirroring LVM
> than
> software.RAID+LVM ?
useing LVM over soft RAID adds extra overhead,  is more CPU intensive

> i think the reason is LVM it does not matter where the disks are at
> all.
> We can do the same with two big external storage towers, not just with
> two
> disks.
> 
> but i think this reason is not enough, can anyone give me some support?
> and how many people use striping or mirroring LVM£¬not
> software.RAID+LVM£¿
> 
> 
> TIA for your help and sorry for my poor English.
> 
>