Hi, This is for HVM guests. I''m using LVM at my home setup for my DomUs, but having some issues with "mounting, umounting" the partitions inside the DomUs, as they are actually a disk image. Some of the kernels of my DomU''s don''t have LVM support at all, making it another issue. Why don''t we just use Extended Partitions? What is the added benefit of LVM to us? I read around that it also includes a little overhead. When it comes to extension, shringking, modification etc, extended partitions are just as good, as you can use many proved commercial products to resize your partitions easily. Am I missing something here? Thanks, Emre _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Stefan de Konink
2007-Nov-26 15:30 UTC
Re: [Xen-users] why LVM? why not Extended Partitions?
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Emre Erenoglu schreef:> Am I missing something here?Rereading the partition table probably? (Of course in a static setup you can just use extended partitions...) Stefan -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.7 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFHSuaBYH1+F2Rqwn0RCisbAJ4i7dW0IUvzUL/GLAERjhUgiYWWGQCfVoES MmAEeSCEmAM0glsCmLO/q80=38gt -----END PGP SIGNATURE----- _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Tomasz Chmielewski
2007-Nov-26 15:38 UTC
Re: [Xen-users] why LVM? why not Extended Partitions?
Emre Erenoglu schrieb:> Hi, > > This is for HVM guests. > > I''m using LVM at my home setup for my DomUs, but having some issues with > "mounting, umounting" the partitions inside the DomUs, as they are > actually a disk image. Some of the kernels of my DomU''s don''t have LVM > support at all, making it another issue. > > Why don''t we just use Extended Partitions? What is the added benefit of > LVM to us? I read around that it also includes a little overhead. When > it comes to extension, shringking, modification etc, extended partitions > are just as good, as you can use many proved commercial products to > resize your partitions easily. > > Am I missing something here?Yes, in several points. 1. It''s dom0 which needs LVM support; domUs don''t need it. In fact, whatever you use on dom0 as a storage for domU (LVM, disk, partition, file etc.) doesn''t matter from the domU point of view - in the end, domU sees "a disk" anyway. 2. How many partitions can you have with extended partitions? I think it''s 16 maximum. I also think there is a maximum size (1 or 8 TB, I don''t remember) old-style partitioning can handle. But I guess it won''t matter for smaller setups anyway. Let''s consider you have 3 partitions with different size, and some free space after them: [ A ][ B ][ C ][ free ] You find that partition B is too small, and you want to resize it? Super easy with LVM, and lots of effort when using old-style partitions. Still LVM not fun for you? It has some additional goodies (like snapshots, etc.). -- Tomasz Chmielewski http://wpkg.org _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Well Thanks for the answers. Now it starts to make sense. My problem seems to be related to the fact that my setup is a "home-setup", where I replace my VMWare Workstation with Xen. The problem occurs when you want to use your DomU sometimes as bare-metal and sometimes as a DomU, and if your domU kernel does not have necessary LVM modules and tools. 1) As domU bare-metal kernel can''t see LVM volumes, I''m locked up at boot on bare-metal. 2) Even though DomU kernel has LVM, when you try to run it on bare-metal, you can''t use LVM as a whole disk image, you can just use it like a partition. A disk image with partitions, inside a LVM volume, can''t be easily mounted if I''m not wrong. Another point maybe related to my setup, is that my LVM volume group is fully utilized and when I need to resize or shrink, I''m having a lot of trouble. I guess I need to read more about LVM. Thanks a lot for the responses. Br, Emre On Nov 26, 2007 4:38 PM, Tomasz Chmielewski <mangoo@wpkg.org> wrote:> Emre Erenoglu schrieb: > > Hi, > > > > This is for HVM guests. > > > > I''m using LVM at my home setup for my DomUs, but having some issues with > > "mounting, umounting" the partitions inside the DomUs, as they are > > actually a disk image. Some of the kernels of my DomU''s don''t have LVM > > support at all, making it another issue. > > > > Why don''t we just use Extended Partitions? What is the added benefit of > > LVM to us? I read around that it also includes a little overhead. When > > it comes to extension, shringking, modification etc, extended partitions > > are just as good, as you can use many proved commercial products to > > resize your partitions easily. > > > > Am I missing something here? > > Yes, in several points. > > 1. It''s dom0 which needs LVM support; domUs don''t need it. In fact, > whatever you use on dom0 as a storage for domU (LVM, disk, partition, > file etc.) doesn''t matter from the domU point of view - in the end, domU > sees "a disk" anyway. > > 2. How many partitions can you have with extended partitions? I think > it''s 16 maximum. I also think there is a maximum size (1 or 8 TB, I > don''t remember) old-style partitioning can handle. > But I guess it won''t matter for smaller setups anyway. > > Let''s consider you have 3 partitions with different size, and some free > space after them: > > [ A ][ B ][ C ][ free ] > > You find that partition B is too small, and you want to resize it? Super > easy with LVM, and lots of effort when using old-style partitions. > > Still LVM not fun for you? It has some additional goodies (like > snapshots, etc.). > > > -- > Tomasz Chmielewski > http://wpkg.org > >-- Emre Erenoglu erenoglu@gmail.com _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Mark Williamson
2007-Nov-27 22:19 UTC
Re: [Xen-users] why LVM? why not Extended Partitions?
> My problem seems to be related to the fact that my setup is a "home-setup", > where I replace my VMWare Workstation with Xen. The problem occurs when you > want to use your DomU sometimes as bare-metal and sometimes as a DomU, and > if your domU kernel does not have necessary LVM modules and tools.Ah OK. We usually recommend LVM in dom0 for managing domU storage. I generally suggest that if people are doing that they don''t want to run LVM in the domU, because then you have two levels of LVM and it makes things confusing to work with. If you want to have a guest that''s either a domU or a bare-metal OS then I agree that using normal partitions is better. This is what we used to do when testing out Xen guests and it worked fairly well at the time. I''d recommend that you abandon using LVM for your purposes (at least for the time being) in order to make things easier for yourself whilst you sort out whatever other problems you come up with. If you''re not wanting to do stuff like resizing volumes, it doesn''t really matter what you''re using anyhow. Cheers, Mark> 1) As domU bare-metal kernel can''t see LVM volumes, I''m locked up at boot > on bare-metal. > 2) Even though DomU kernel has LVM, when you try to run it on bare-metal, > you can''t use LVM as a whole disk image, you can just use it like a > partition. A disk image with partitions, inside a LVM volume, can''t be > easily mounted if I''m not wrong. > > Another point maybe related to my setup, is that my LVM volume group is > fully utilized and when I need to resize or shrink, I''m having a lot of > trouble. I guess I need to read more about LVM. > > Thanks a lot for the responses. > > Br, > > Emre > > On Nov 26, 2007 4:38 PM, Tomasz Chmielewski <mangoo@wpkg.org> wrote: > > Emre Erenoglu schrieb: > > > Hi, > > > > > > This is for HVM guests. > > > > > > I''m using LVM at my home setup for my DomUs, but having some issues > > > with "mounting, umounting" the partitions inside the DomUs, as they are > > > actually a disk image. Some of the kernels of my DomU''s don''t have LVM > > > support at all, making it another issue. > > > > > > Why don''t we just use Extended Partitions? What is the added benefit of > > > LVM to us? I read around that it also includes a little overhead. When > > > it comes to extension, shringking, modification etc, extended > > > partitions are just as good, as you can use many proved commercial > > > products to resize your partitions easily. > > > > > > Am I missing something here? > > > > Yes, in several points. > > > > 1. It''s dom0 which needs LVM support; domUs don''t need it. In fact, > > whatever you use on dom0 as a storage for domU (LVM, disk, partition, > > file etc.) doesn''t matter from the domU point of view - in the end, domU > > sees "a disk" anyway. > > > > 2. How many partitions can you have with extended partitions? I think > > it''s 16 maximum. I also think there is a maximum size (1 or 8 TB, I > > don''t remember) old-style partitioning can handle. > > But I guess it won''t matter for smaller setups anyway. > > > > Let''s consider you have 3 partitions with different size, and some free > > space after them: > > > > [ A ][ B ][ C ][ free ] > > > > You find that partition B is too small, and you want to resize it? Super > > easy with LVM, and lots of effort when using old-style partitions. > > > > Still LVM not fun for you? It has some additional goodies (like > > snapshots, etc.). > > > > > > -- > > Tomasz Chmielewski > > http://wpkg.org-- Dave: Just a question. What use is a unicyle with no seat? And no pedals! Mark: To answer a question with a question: What use is a skateboard? Dave: Skateboards have wheels. Mark: My wheel has a wheel! _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users