[linux-lvm] Some questions after starting to use 1.1-rc1

Piete Brooks Piete.Brooks at cl.cam.ac.uk
Thu Apr 25 16:32:02 UTC 2002

>> 1) I've been comparing the speed of LVM over RAID0 with striped LVM, using:
>> 	perl -e '$n=1900;$x="X"x(1024*1024);foreach $i(1..$n){print $x}'
>>    and I find that striped LVM takes 50% longer.
> which stripe size did you use?

I don't think I specified -- so "the default" ?

> Were the PVs on non-saturated pathes?

What are "non-saturated pathes" ?

There were two PVs, each on an otherwise unused IDE bus.

> Did you compare LVM1 Raid0 to MD Raid0 on the very same hardware?


>> 2) When I tried to extend the striped partition, it failed when it used up
>>    the first two PVs, and will not start the next two.  Ideas ?
> That's a LVM1 constraint which will disapear with LVM2.


Is there an introductory document on device-mapper ?

> No need to vgexport to test it.

Hmmm ...

> Just stop one PV as you did

stop the RAID device while it's in use by LVM ?

>>     b) should it be possible to export a VG if there is a PV of that VG 
>>       is still exported ?


>> 5) is there some utility to display the contents of VGDA on disk, /etc/lvm*,
>>    etc;  show where the first PE is in a PV, etc ? 
> Run "pvdata -a" on the particular PV.

Where does it say "PE 0 starts at byte offset <n> of the device" ?

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