Lustre discuss - May 2006 - Why two osc and lov for one ost setup?

On Sep 21, 2005  17:40 -0500, Dingshan He wrote:
> I am testing with the following simple one node with one client, one ost
and
> one mds configuration.
> 
> 	../utils/lmc -m local.xml --add node --node localhost
> 	../utils/lmc -m local.xml --add net --node localhost --nid localhost
> --nettype tcp
> 	
> 	../utils/lmc -m local.xml --format --add mds --node localhost --mds
> mds-test --fstype ext3 --dev /tmp/mds-test --size 50000
> 	
> 	../utils/lmc -m local.xml --add ost --node localhost --ost ost1-test
> --fstype ext3 --dev /tmp/ost1-test --size 100000
> 	
> 	../utils/lmc -m local.xml --add mtpt --node localhost --path
> /mnt/lustre --mds mds-test --ost ost1-test
> 
> After the lustre is up, I used "lctl dl" to list all the obds.
Following is
> what I got:
>   0 UP obdfilter ost1-test ost1-test_UUID 3
>   1 UP ost OSS OSS_UUID 1
>   2 UP mdt MDT MDT_UUID 1
>   3 UP mds mds-test mds-test_UUID 2
>   4 UP osc OSC_localhost.localdomain_ost1-test_mds-test
> cfddc486-602e-4f1a-889c-069caf591fba 2
>   5 UP lov lov_mds-test cfddc486-602e-4f1a-889c-069caf591fba 2
>   6 UP osc OSC_localhost.localdomain_ost1-test_MNT_localhost
> ad4e0_lov_default_19598ebe23 2
>   7 UP lov lov_default ad4e0_lov_default_19598ebe23 2
>   8 UP mdc MDC_localhost.localdomain_mds-test_MNT_localhost
> eaea1_MNT_localhost_cbd393332b 2
> 
> My question is why there are two pairs of (lov, osc), i.e., (4,5) and
(6,7)?
> The pair (6,7) seems to be what is specified in the configuration file.
What
> is the pair (4,5) used for?
If you look closely at the OBD names, the pair (4,5) are for the MDS
(mds-test), and the pair (6,7) are for the client mount (MNT_localhost).

The MDS needs a connection to the OSTs in order to manage objects there
during recovery.  In the (nearish) future it will also use statfs data
from the OSTs in order to more uniformly allocate new files to OSTs
which have more free space.

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

Hello,

I am testing with the following simple one node with one client, one ost and
one mds configuration.

	../utils/lmc -m local.xml --add node --node localhost
	../utils/lmc -m local.xml --add net --node localhost --nid localhost
--nettype tcp
	
	../utils/lmc -m local.xml --format --add mds --node localhost --mds
mds-test --fstype ext3 --dev /tmp/mds-test --size 50000
	
	../utils/lmc -m local.xml --add ost --node localhost --ost ost1-test
--fstype ext3 --dev /tmp/ost1-test --size 100000
	
	../utils/lmc -m local.xml --add mtpt --node localhost --path
/mnt/lustre --mds mds-test --ost ost1-test

After the lustre is up, I used "lctl dl" to list all the obds.
Following is
what I got:
  0 UP obdfilter ost1-test ost1-test_UUID 3
  1 UP ost OSS OSS_UUID 1
  2 UP mdt MDT MDT_UUID 1
  3 UP mds mds-test mds-test_UUID 2
  4 UP osc OSC_localhost.localdomain_ost1-test_mds-test
cfddc486-602e-4f1a-889c-069caf591fba 2
  5 UP lov lov_mds-test cfddc486-602e-4f1a-889c-069caf591fba 2
  6 UP osc OSC_localhost.localdomain_ost1-test_MNT_localhost
ad4e0_lov_default_19598ebe23 2
  7 UP lov lov_default ad4e0_lov_default_19598ebe23 2
  8 UP mdc MDC_localhost.localdomain_mds-test_MNT_localhost
eaea1_MNT_localhost_cbd393332b 2

My question is why there are two pairs of (lov, osc), i.e., (4,5) and (6,7)?
The pair (6,7) seems to be what is specified in the configuration file. What
is the pair (4,5) used for?

Any comments are highly appreciated!

Dingshan