[linux-lvm] LVM and devices
mauelsha at ez-darmstadt.telekom.de
Sun Aug 29 00:47:10 UTC 1999
> Heinz writes:
> > > I haven't had a chance to
> > > look yet). For that matter, LVM shouldn't be tied to the /dev names of
> > > anything, since you could just start traversing the available devices,
> > > find a list of UUIDs that make up a VG, and not have to worry about the
> > > /dev names of anything (nor even store them anywhere).
> > Actually, it depends on /dev namespace today.
> > But the sole reason for this is perforrmance.
> > We could simply throw that dependency away, if we go devfs or
> > could live with performance impacts without devfs.
> It shouldn't be a big change to have LVM not STORE the device names in
> the VGDA,
It doesn't use a stored devices name in the PV part of the VGDA today.
The device name is inserted at PV read time (see pv_read()).
> and something like a pvscan is done at boot-time (after the LVM
> module is loaded, if a module) to determine PV -> /dev mapping. The LVM
> kernel code would still use the device name/major+minor in memory to
> access the devices, so there should be no performance impact outside a
> small amount of scanning at boot time or when a new VG is imported.
What i meant with performance impact is the longer time to scan large
/dev configurations in user space (vgscan, pvscan and friends).
Systemmanagement CS-TS T-Nova
Heinz Mauelshagen Otto-Roehm-Strasse 71c
Senior Systems Engineer Postfach 10 05 41
mge at ez-darmstadt.telekom.de Germany
+49 6151 886-425
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