Hi, I''m just wondering if there are any speed or stability differences between running a system directly of a LVM partition versus a xvd partition? Basicly: disk = [ ''phy:/dev/LVM/root,xvda,w'', ] vs disk= [ ''phy:LVM/root,hda1,w'',] Any tips? I tried searching the archives but I didn''t find anything. Kind regards, Tarjei _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> Hi, I''m just wondering if there are any speed or stability differences > between running a system directly of a LVM partition versus a xvd > partition? >I''m a little confused about what you''re asking, so I''ll explain a few things and hopefully it''ll help some. Please ask again if I''m not answering the questions you wanted.> Basicly: > disk = [ ''phy:/dev/LVM/root,xvda,w'', ]This exports /dev/LVM/root as the whole disk device /dev/xvda in the guest.> disk= [ ''phy:LVM/root,hda1,w'',]This exports /dev/LVM/root (as before) as the partition /dev/hda1 in the guest. So, whether or not you include /dev in the device path, you''re still exporting the same device. As to whether to export a whole device or a partition... Exporting as a single partition (e.g. /dev/hda1 in your example) has the advantage that /dev/LVM/root will be directly mountable in dom0 because it will not have been partitioned by the guest. The guest won''t be allowed to repartition /dev/hda, it''ll be stuck with one partition there. Exporting as a whole device gives the guest flexibility to partition its VBD as it sees fit but means it''s slightly less convenient to mount /dev/LVM/root in dom0 (but there are tools to read the partition and make this easy for you). I usually go for the latter approach, but it doesn''t matter in terms of speed and stability. It''s really quest a question of administration convenience and how you want things to look like the guest. Cheers, Mark -- 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
Hi, Mark Williamson wrote:>> Hi, I''m just wondering if there are any speed or stability differences >> between running a system directly of a LVM partition versus a xvd >> partition? >> >> I''m a little confused about what you''re asking, so I''ll explain a few things >> and hopefully it''ll help some. Please ask again if I''m not answering the >> questions you wanted. >>I was mainly wondering about the speed issues involved in the two approaches. Since I didn''t hear anything the first few days, I also asked on #xen where I was told that there isn''t any performance overhead and that overloading the normal disk, say /dev/hda1, will be phased out in the future. Thank you for your answer. Kind regards, Tarjei>> Basicly: >> disk = [ ''phy:/dev/LVM/root,xvda,w'', ] >> > > This exports /dev/LVM/root as the whole disk device /dev/xvda in the guest. > > >> disk= [ ''phy:LVM/root,hda1,w'',] >> > > This exports /dev/LVM/root (as before) as the partition /dev/hda1 in the > guest. > > So, whether or not you include /dev in the device path, you''re still exporting > the same device. > > As to whether to export a whole device or a partition... > > Exporting as a single partition (e.g. /dev/hda1 in your example) has the > advantage that /dev/LVM/root will be directly mountable in dom0 because it > will not have been partitioned by the guest. The guest won''t be allowed to > repartition /dev/hda, it''ll be stuck with one partition there. > > Exporting as a whole device gives the guest flexibility to partition its VBD > as it sees fit but means it''s slightly less convenient to mount /dev/LVM/root > in dom0 (but there are tools to read the partition and make this easy for > you). > > I usually go for the latter approach, but it doesn''t matter in terms of speed > and stability. It''s really quest a question of administration convenience > and how you want things to look like the guest. > > Cheers, > Mark > >_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> -----Original Message----- > From: xen-users-bounces@lists.xensource.com > [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of tarjei > Sent: 25 April 2007 07:19 > To: Mark Williamson > Cc: xen-users@lists.xensource.com > Subject: Re: [Xen-users] xvda vs lvm > > Hi, > Mark Williamson wrote: > >> Hi, I''m just wondering if there are any speed or stability > differences > >> between running a system directly of a LVM partition versus a xvd > >> partition? > >> > >> I''m a little confused about what you''re asking, so I''ll > explain a few things > >> and hopefully it''ll help some. Please ask again if I''m > not answering the > >> questions you wanted. > >> > I was mainly wondering about the speed issues involved in the two > approaches. Since I didn''t hear anything the first few days, I also > asked on #xen where I was told that there isn''t any > performance overhead > and that overloading the normal disk, say /dev/hda1, will be > phased out > in the future.Yes, there shouldn''t be any difference, as the same interface/code-path is being used for both operations, it''s just the actual name of the device inside the guest that is different... -- Mats _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
On Wed, Apr 25, 2007 at 08:18:38AM +0200, tarjei wrote:> Hi, > Mark Williamson wrote: > >>Hi, I''m just wondering if there are any speed or stability differences > >>between running a system directly of a LVM partition versus a xvd > >>partition? > >> > >>I''m a little confused about what you''re asking, so I''ll explain a few > >>things and hopefully it''ll help some. Please ask again if I''m not > >>answering the questions you wanted. > >> > I was mainly wondering about the speed issues involved in the two > approaches. Since I didn''t hear anything the first few days, I also > asked on #xen where I was told that there isn''t any performance overhead > and that overloading the normal disk, say /dev/hda1, will be phased out > in the future.That doesn''t make any sense - the same driver code is used to access both LVM partitions & regular partitions. LVM does add one extra layer in the kernel I/O stack compared to directly using regular paritions, but the performance difference would be pretty small. I can''t imagine any difference being a problem for the vast majority of users, particularly given the flexibilty LVM adds for management. There are still use cases for regular partitions - eg SAN where the volume allocation/management is done directly at the SAN rather than the host thus making LVM less compelling. Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=| _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users