* [linux-lvm] Re: Welcome to the "linux-lvm" mailing list [not found] <mailman.11694.1112144246.19557.linux-lvm@redhat.com> @ 2005-03-30 1:02 ` Andy Sy 2005-03-30 6:52 ` Luca Berra 0 siblings, 1 reply; 4+ messages in thread From: Andy Sy @ 2005-03-30 1:02 UTC (permalink / raw) To: linux-lvm Just like the kernel is now able to autodetect and autoenable md RAID arrays, are there plans to make lvm do the same? (i.e integrate the functionality of vgscan / vgchange -ay,-an into the kernel) If lvm really introduces as negligible an overhead as it is touted to, there really seems to be no reason to go with 'physical' partitions anymore and it should go the way of the dodo. I can see a future where everyone installs their Linux distros on logical volumes. ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [linux-lvm] Re: Welcome to the "linux-lvm" mailing list 2005-03-30 1:02 ` [linux-lvm] Re: Welcome to the "linux-lvm" mailing list Andy Sy @ 2005-03-30 6:52 ` Luca Berra 2005-03-30 15:38 ` [linux-lvm] Re: putting lvm autodetect into the kernel ala md Andy Sy 0 siblings, 1 reply; 4+ messages in thread From: Luca Berra @ 2005-03-30 6:52 UTC (permalink / raw) To: linux-lvm On Wed, Mar 30, 2005 at 09:02:28AM +0800, Andy Sy wrote: >Just like the kernel is now able to autodetect and >autoenable md RAID arrays, are there plans to make kernel autodetection of md arrays is almost always a bad idea, it is far better to use mdadm in user space for that. >lvm do the same? (i.e integrate the functionality >of vgscan / vgchange -ay,-an into the kernel) no, it is an user space task, there is no reason to burden the kernel with this. a different thing my be said for kernel level manual configuration (the md=....) commandline, but i dont' feel the need to implement a device mapper kernel commandline to achieve this. L. -- Luca Berra -- bluca@comedia.it Communication Media & Services S.r.l. /"\ \ / ASCII RIBBON CAMPAIGN X AGAINST HTML MAIL / \ ^ permalink raw reply [flat|nested] 4+ messages in thread
* [linux-lvm] Re: putting lvm autodetect into the kernel ala md 2005-03-30 6:52 ` Luca Berra @ 2005-03-30 15:38 ` Andy Sy 2005-03-31 7:38 ` Luca Berra 0 siblings, 1 reply; 4+ messages in thread From: Andy Sy @ 2005-03-30 15:38 UTC (permalink / raw) To: LVM general discussion and development Luca Berra wrote: > >Just like the kernel is now able to autodetect and > >autoenable md RAID arrays, are there plans to make > kernel autodetection of md arrays is almost always a > bad idea, it is far better to use mdadm in user space for that. Why is this necessarily so? RAID autodetect seems to avoid a lot of configuration hassles especially when your root partition is involved. Any horror stories to tell? > >lvm do the same? (i.e integrate the functionality > >of vgscan / vgchange -ay,-an into the kernel) > no, it is an user space task, there is no reason to > burden the kernel with this. People have recommended against using an LVM volume for your root partition citing the hassle of a rescue disk as being the main reason. If lvm volume autodetect and enabling were in the kernel, then this would no longer be the case. I have a good reason for wanting my root partition to be a logical volume: this is because I can install my distro directly into it one single big logical volume and only have to worry about how to repartition it later in the game. Being unable to use a logical volume as root partition is very inconvenient because you have to make an early decision regarding which of your top-level directories (i.e. /usr, /home, /var, /opt, /tmp) to turn into logical volumes and which ones to put on physical partitions. Worse, as far as I can tell, you are forced to allocate one logical volume per top-level dir. This means you are unable to share logical volume space among directories for which it makes sense to (e.g. /opt and /usr), thus you might find yourself resizing logical volumes more often than you wish down the line. If lvm were stable and mature enough, and if the claism being made for it as having very low overhead area are accurate, the logical conclusion (no pun intended) would be for people to eventually stop using physical partitions and using volume groups from the get-go. Unless lvm detect/enable functionality were built into the kernel though, you will always have to live with a physical partition holding /boot - the case today with LVM and RAID0, but not RAID1 (from which it is possible to boot directly off of). ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [linux-lvm] Re: putting lvm autodetect into the kernel ala md 2005-03-30 15:38 ` [linux-lvm] Re: putting lvm autodetect into the kernel ala md Andy Sy @ 2005-03-31 7:38 ` Luca Berra 0 siblings, 0 replies; 4+ messages in thread From: Luca Berra @ 2005-03-31 7:38 UTC (permalink / raw) To: LVM general discussion and development On Wed, Mar 30, 2005 at 11:38:16PM +0800, Andy Sy wrote: >Luca Berra wrote: > >> >Just like the kernel is now able to autodetect and >> >autoenable md RAID arrays, are there plans to make > >> kernel autodetection of md arrays is almost always a >> bad idea, it is far better to use mdadm in user space for that. > >Why is this necessarily so? RAID autodetect seems to >avoid a lot of configuration hassles especially when your >root partition is involved. Any horror stories to tell? yes, read the linux-raid mailing list for those, i am tired of beating the same dead horse. >> >lvm do the same? (i.e integrate the functionality >> >of vgscan / vgchange -ay,-an into the kernel) > >> no, it is an user space task, there is no reason to >> burden the kernel with this. > >People have recommended against using an LVM >volume for your root partition citing the hassle of >a rescue disk as being the main reason. If lvm volume this is just ridicolous fud. in what cases you would need a rescue disk? are those really different from the cases you'd need a rescue disk for a normal partition-table based system. besides, every live distro on earth now supports lvm and can be used as a recovery tool. >autodetect and enabling were in the kernel, then >this would no longer be the case. why? >I have a good reason for wanting my root partition >to be a logical volume: this is because I can i have been using my root partition as a logical volume for several years now. >Unless lvm detect/enable functionality were built into >the kernel though, you will always have to live with a >physical partition holding /boot - the case today >with LVM and RAID0, but not RAID1 (from which it is >possible to boot directly off of). i don't have a separate partition for /boot on my lvm systems. the only reason i needed a separate boot partition was when i had a system using raid5, so i had to have a separate raid1 partition for booting. Reading your arguments it appeare you are mis-informed and make a lot of confusion between a boot loader (which is the only limitation we have in loading a kernel/initrd/initramfs) and what the kernel can do. Regards, Luca -- Luca Berra -- bluca@comedia.it Communication Media & Services S.r.l. /"\ \ / ASCII RIBBON CAMPAIGN X AGAINST HTML MAIL / \ ^ permalink raw reply [flat|nested] 4+ messages in thread
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[not found] <mailman.11694.1112144246.19557.linux-lvm@redhat.com>
2005-03-30 1:02 ` [linux-lvm] Re: Welcome to the "linux-lvm" mailing list Andy Sy
2005-03-30 6:52 ` Luca Berra
2005-03-30 15:38 ` [linux-lvm] Re: putting lvm autodetect into the kernel ala md Andy Sy
2005-03-31 7:38 ` Luca Berra
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