[linux-lvm] lvm pvscan or vgscan very slow

[linux-lvm] lvm pvscan or vgscan very slow

[Ling Li]

I am using Fedora 1 with some packages updated from the fedora 
development in order to use kernel 2.6 and LVM2. The operation `lvm 
pvscan' and `lvm vgscan' are very slow, taking about 20-30 min. Is this 
normal, or is this because there is no /etc/lvm.conf file?

Here are the system settings:

device-mapper-1.00.07-2
kernel-smp-2.6.1-1.65
lvm-1.0.3-17
lvm2-2.00.08-2
mkinitrd-3.5.19-1

Root partitions on a SCSI disk, no LVM.
Some data partitions on an 80G IDE disk, with LVM2: 1 PV  1 VG  3 LVs.

--Ling

Re: [linux-lvm] lvm pvscan or vgscan very slow

[Alasdair G Kergon]

On Thu, Feb 12, 2004 at 03:33:57PM -0800, Ling Li wrote:
> I am using Fedora 1 with some packages updated from the fedora 
> development in order to use kernel 2.6 and LVM2. The operation `lvm 
> pvscan' and `lvm vgscan' are very slow, taking about 20-30 min. Is this 
> normal, or is this because there is no /etc/lvm.conf file?
 
It shouldn't be that slow!

Look at your system log and/or run with -vvv to see why it's so slow.

We've a couple of speed-ups that might help (one uses sysfs to reduce
the number of devices to scan) - they're in the queue of things waiting
to be checked into CVS after the repository move.
I'll try to get them imported tomorrow.
 
Alasdair
-- 
agk@redhat.com

Re: [linux-lvm] lvm pvscan or vgscan very slow

[Ling Li]

Alasdair G Kergon wrote:
> It shouldn't be that slow!
> Look at your system log and/or run with -vvv to see why it's so slow.

# lvm pvscan -vvv > ~/pvscan-list
# grep "Added to device cache" pvscan-list  | wc -l
   15813

I guess the number of devices to be scanned is just too large (and my 
computer is also a very slow one). Is there some way to specify a 
narrower range of devices to be scanned in LVM2?

> We've a couple of speed-ups that might help (one uses sysfs to reduce
> the number of devices to scan) - they're in the queue of things waiting
> to be checked into CVS after the repository move.
> I'll try to get them imported tomorrow.
This kind of patch will definitely help!

--Ling

Re: [linux-lvm] lvm pvscan or vgscan very slow

[Alasdair G Kergon]

On Fri, Feb 13, 2004 at 03:28:19PM -0800, Ling Li wrote:
> I guess the number of devices to be scanned is just too large (and my 
> computer is also a very slow one). Is there some way to specify a 
> narrower range of devices to be scanned in LVM2?
 
The filter lines in lvm.conf.  See doc/example.conf and man lvm.conf.

> > We've a couple of speed-ups that might help (one uses sysfs to reduce
> > the number of devices to scan) - they're in the queue of things waiting
> > to be checked into CVS after the repository move.
> > I'll try to get them imported tomorrow.
> This kind of patch will definitely help!
 
Both changes are in CVS now.

Info on how to get code out of CVS:
  http://www.sistina.com/products_CVS.htm
BUT replace the 'cvs -d :pserver:' lines with those shown on:
  http://sources.redhat.com/lvm2/

Alasdair
-- 
agk@redhat.com

Re: [linux-lvm] lvm pvscan or vgscan very slow

[Ling Li]

Alasdair G Kergon wrote:
> On Fri, Feb 13, 2004 at 03:28:19PM -0800, Ling Li wrote:
> 
>>I guess the number of devices to be scanned is just too large (and my 
>>computer is also a very slow one). Is there some way to specify a 
>>narrower range of devices to be scanned in LVM2?
> 
>  
> The filter lines in lvm.conf.  See doc/example.conf and man lvm.conf.

Got it. The man page says lvm.conf is only loaded during the 
"initialization phase of LVM." Does this mean I have to reboot the 
computer for the new lvm.conf to be in effect? Can I just send some 
signal to some process?

--Ling

Re: [linux-lvm] lvm pvscan or vgscan very slow

[Heinz Mauelshagen]

On Fri, Feb 13, 2004 at 04:07:34PM -0800, Ling Li wrote:
> 
> 
> Alasdair G Kergon wrote:
> >On Fri, Feb 13, 2004 at 03:28:19PM -0800, Ling Li wrote:
> >
> >>I guess the number of devices to be scanned is just too large (and my 
> >>computer is also a very slow one). Is there some way to specify a 
> >>narrower range of devices to be scanned in LVM2?
> >
> > 
> >The filter lines in lvm.conf.  See doc/example.conf and man lvm.conf.
> 
> Got it. The man page says lvm.conf is only loaded during the 
> "initialization phase of LVM." Does this mean I have to reboot the 
> computer for the new lvm.conf to be in effect? Can I just send some 
> signal to some process?

No, just run vgscan after setting up your filter in lvm.conf.

> 
> --Ling
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

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Heinz Mauelshagen                                 Red Hat, Inc.
Consulting Development Engineer                   Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen@RedHat.com                            +49 2626 141200
                                                       FAX 924446
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