You also have to remember that in most LVM implementations adding a device to the
LVM does not add it to the raid.
For example, let's say we have a raid1 array with 2 devices on it, and we have
assigned the array to be part of an LVM. Now, let's say you add a 3rd drive. At
this point you have not added the device to the raid1 array, but only to the lvm
volume group, thusly there will be no redundancy apon the device. LVM+Raid
support comes in handy when you want to clunk together groups of raid arrays. But
bare in mind that it wont necessarily make your life easier .. in putting an LVM
layer over the top of raid you can actually force yourself into greater
restrictions about how you can use the device.
"Oh look .. the 90G raid5 array is getting pretty full .. I guess we should add
more drives to it .. oh .. hold it .. it's a raid5 .. we can't just add more space
to it .. we have to LVM attach another raid5 array to the array in order to keep
redundancy"
The ability to add/remove/resize the lower level raid enviroment would be in my
opinion alot more beneficial in the long run if it is possible.
Jakob Østergaard wrote:
> On Tue, Nov 02, 1999 at 01:56:06PM +0100, Egon Eckert wrote:
> > > There's a new version of the raidreconf utility out. I call it 0.0.2.
> >
> > Isn't this what supposed 'LVM' to be about? (BTW there seem to be 2
> > different implementations of LVM on the web -- one included in 0.90 raid
> > patch and one on http://linux.msede.com/lvm/)
>
> Well, yes and no. LVM gives you pretty much the same features, the ability
> to add disks to a device to grow it.
>
> The only reason I started the raidreconf utility was, because I needed to be
> able to add/remove disks from RAID arrays *today*. LVM is, from what I can
> understand, still not implemented to a state where you can use it and rely
> on it. I know I can rely on the RAID code in the kernel, so all I was missing
> was a utility to add/remove disks from RAID sets. Now I have one, at least
> for RAID-0 :)
>
> While I'm at it, I hope to build in some conversion features too, so that you
> can convert between RAID levels. The utility can already convert a single
> block device into a RAID-0, but being able to convert a five disk RAID-0 into
> eg. a seven disk RAID-5 would be pretty sweet I guess. Remember, this is all
> functionality that, once raidreconf works, is perfectly stable and well tested,
> because all the ``real'' support for the RAID levels has been in the kernels or
> at least the patches for a long time now.
>
> > Can someone clarify this?
> >
> > A few months ago I asked what's the 'translucent' feature as well, but no
> > reply.. :(
>
> I would actually like to know about the state of LVM, HSM, and all the other
> nice storage features being worked on in Linux. I wouldn't want to spend time
> on this utility if it was entirely redundant. But then again, I don't think it
> is, at this time. Hopefully, in a year or so, nobody will care about
> raidreconf, because we have LVM working and providing even more features. Or
> maybe some raidreconf code could be used for the LVM for providing the
> conversion features.
>
> Time will show :)
>
> --
> ................................................................
> : [EMAIL PROTECTED] : And I see the elder races, :
> :.........................: putrid forms of man :
> : Jakob Østergaard : See him rise and claim the earth, :
> : OZ9ABN : his downfall is at hand. :
> :.........................:............{Konkhra}...............:
--
Mark Ferrell : [EMAIL PROTECTED]
(972) 685-7868 : Desk
(972) 685-4210 : Lab
(972) 879-4326 : Pager
