Re: [RFC] LVM/RAID/FS integration



Kent Overstreet wrote:
The trouble is it's completely impractical with current tools; we need
tighter integration between md and LVM. Basically, we need a new type
of VG; you'd only be able to make it out of PVs that are the same size
(or close). Then, when you create an LV you decide what kind of
redundancy you want; the LVM internally creates multiple LVs and raids
them together to make the LV the fs sees.

In theory LVM is meant to handle the raid bits as well, once the mirror target is improved to properly handle error correction, and the raid5 target stabilizes. Thus md won't be needed, you will just need an interface between the filesystem and lvm.

This could, sort of, be done in userspace, but I think it'll work
better if dm and md are better integrated in the kernel. I thought i'd
throw out my ideas before I get too far in. Thoughts?

This is the kind of thing that should go in userspace. The filesystem should just fire off events that tell a userspace daemon things like "the raid5 volume is now at x% use" and let it choose the policy, possibly by asking lvm to resize the underlying volume, then sending a message back to the fs that the volume has been resized, and it can start using the extra space.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/



Relevant Pages

  • Re: Wheres ext2online?
    ... saying it couldn't unmount the root filesystem. ... the executable lvm is, which can do all those things. ... you will get a new prompt, where you type lvm commands. ... I was able to resize the mounted filesystem without going into rescue mode. ...
    (Fedora)
  • Re: resizing swap
    ... Otherwise you wouldnt be able to fsck a filesystem without external boot. ... Write the FC rescue disk ISO onto a CD, and reboot the machine from it. ... Within LVM, run these commands: ... Now resize the filesystem with this command ...
    (RedHat)
  • Re: resizing swap
    ... You can't shrink a volume using resize2fs so rebooting into single user mode and mounting / as read-only won't work. ... Write the FC rescue disk ISO onto a CD, and reboot the machine from it. ... Within LVM, run these commands: ... Now resize the filesystem with this command (e.g., ...
    (RedHat)
  • RE: resizing swap
    ... At the prompt, type: ... Within LVM, run these commands: ... Now resize the filesystem with this command (e.g., ...
    (RedHat)
  • Re: Booting - Enterprise Volume Management System
    ... it seems that LVM combines the main ... disadvantage of separate partitions - having to manually unmount and resize when ... you run out of space - with the main disadvantage of one big partition - ... The main advantage appears being able to resize logical volumes and filesystems ...
    (Ubuntu)