Accurately Time Your Parallel Loops in OpenMP

Learn how to use a wall clock timer that is included as part of the OpenMP library. Jeff Cogswell walks you through how. Taken from Accurately Time Your Parallel Loops in OpenMP which is found http://goparallel.sourceforge.net/

NFS mount errors with “clnt_create: RPC: Unknown host” for CentOS 6

When attempting to mount CentOS 6, my mount fails with

clnt_create: RPC: Unknown host

Diagnostic:

If we do a more thorough diagnostic, this is the issue

# showmount -e  
clnt_create: RPC: Unknown host  
# showmount -e localhost  
Export list for localhost:  
/export/my_data \*

Resolution:

Taken from Redhat Site

Implement forward and reverse lookups (A records and CNAME records) in DNS and have the system point towards the DNS servers. Implement for both IPv4 and IPv6. If unable to resolve DNS issues, change the /etc/hosts file from this:

Change from

::1          localhost localhost.localdomain localhost6 localhost6.localdomain6

To

::1          machine_hostname localhost localhost.localdomain localhost6 localhost6.localdomain6

Restart the NFS service and check on the showmount -e localhost and showmount -e and attempt to mount the share.

# service nfs restart  
# showmount -e localhost  
# showmount -e

Assigning ownership to disks for NetApp OnTap 8.2p2 Cluster mode

After replacing broken disks for NetApp Storage and if you want to manually assigned ownership back to the newly replaced but assigned disks, you can use the following command

1. Show Storage Ownership Information

My-NetApp-Cluster::> storage disk show -spare
Original Owner: acai-cluster1-01
  Checksum Compatibility: block
                                                            Usable Physical
    Disk            HA Shelf Bay Chan   Pool  Type    RPM     Size     Size Owner
    --------------- ------------ ---- ------ ----- ------ -------- -------- --------
    cluster1-01:0b.00.9
                    0b     0   9    B  Pool0  BSAS   7200   1.62TB   1.62TB cluster1-01
Original Owner: cluster1-02
  Checksum Compatibility: block
                                                            Usable Physical
    Disk            HA Shelf Bay Chan   Pool  Type    RPM     Size     Size Owner
    --------------- ------------ ---- ------ ----- ------ -------- -------- --------
    cluster1-02:0a.00.7
                    0a     0   7    B  Pool0  BSAS   7200   1.62TB   1.62TB cluster1-02
.....
.....

2. Display all unowned disks by entering the following command:

My-NetApp-Cluster::> storage disk show -container-type unassigned


                     Usable           Container
Disk                   Size Shelf Bay Type        Position   Aggregate Owner
---------------- ---------- ----- --- ----------- ---------- --------- --------
cluster1-01:0b.00.9
                     1.62TB     0   9 spare       present    -         cluster1-01
cluster1-02:0a.00.7
                     1.62TB     0   7 spare       present    -         cluster1-02

3. Assign each disk by entering the following command

My-NetApp-Cluster::> storage disk assign -disk cluster1-01:0b.00.9 -owner cluster1-01

Identify broken disk for NetApp OnTap 8.2p2 Cluster mode

1. Identify the Cluster Nodes

My-NetApp-Cluster::> cluster show

Node                  Health  Eligibility
--------------------- ------- ------------
cluster1-01      true    true
cluster1-02      true    true
cluster1-03      true    true
cluster1-04      true    true
4 entries were displayed.

2. Check for Broken Disk

My-NetApp-Cluster::> run -node cluster1-01 vol status -f
RAID Disk Device   HA  SHELF BAY CHAN Pool Type  RPM  Used (MB/blks)    Phys (MB/blks)
--------- ------   ------------- ---- ---- ---- ----- --------------    --------------
failed   0a.00.12 0a    0   12  SA:A   -  BSAS  7200 1695466/3472315904 1695759/3472914816 
failed   0b.00.9  0b    0   9   SA:B   -  BSAS  7200 1695466/3472315904 1695759/3472914816

3. Get System Information

My-NetApp-Cluster::> run -node cluster1-01 sysconfig -a
NetApp Release 8.2P2 Cluster-Mode: Sat Jul 20 20:31:47 PDT 2013
.....
.....
.....

4. Get further Information

My-NetApp-Cluster::> run -node cluster1-01 sysconfig -r
Aggregate storage1_aggr1 (online, mixed_raid_type, hybrid) (block checksums)
.....
.....

Create export domain or ISO Domain on RHEV 3

This is taken from Red Hat Portal How to create an export domain or iso domain? (Need customer access)

On the NFS, you need to do the following

# mkdir /export/data
# chown -R 36:36 /export/data
# chmod 755 /export/data
# vim /export_data
/export/data *(rw)
# /etc/init.d/nfs restart
# chkconfig nfs on

The key setup is that the ownership must be given vdsm kvm (36:36). Or you will have errors like
“Error while executing action Add Storage Connection: Problem while trying to mount target”

# mkdir /export/ISO 
# chown -R 36:36 /export/ISO 
# chmod 755 /export/ISO 
# vim /export/ISO /export/ISO *(rw) 
# /etc/init.d/nfs restart 
# chkconfig nfs on

References:

  1. Red Hat Enterprise Virtualisation and NFS (NetApp Community)
  2. How to create an export domain or iso domain? (Red Hat Portal – Restricted Access)

Subscribing to Red Hat Virtualisation Manager Channels

Taken from Red Hat Red Hat Enterprise Visualization Documentation

Step 1: Register the system with Subscription Manager
Run the following command and enter your Red Hat Network user name and password to register the system with the Red Hat Network

subscription-manager register

Step 2: Identify Available Entitlement Pools
Entitlement pools containing the channels required to install the Red Hat Enterprise Virtualization Manager

# subscription-manager list --available | grep -A8 "Red Hat Enterprise Linux Server"
# subscription-manager list --available | grep -A8 "Red Hat Enterprise Virtualization"

Step 3: Attach Entitlement Pools to the System
Use the pool identifiers located in the previous step to attach both the Red Hat Enterprise Linux Server and Red Hat Enterprise Virtualization entitlements to the system. Run the following command to attach the entitlements:

# subscription-manager attach --pool=[POOLID]

Step 4: Enable the Required Channels
Run the following commands to enable the channels required to install Red Hat Enterprise Virtualization:

# yum-config-manager --enable rhel-6-server-rpms
# yum-config-manager --enable rhel-6-server-supplementary-rpms
# yum-config-manager --enable rhel-6-server-rhevm-3.4-rpms
# yum-config-manager --enable jb-eap-6-for-rhel-6-server-rpms