Recent Posts by Alejandro Vargas

Kerberos and Sentry help us defining access privileges for a limited set of object living on HDFS We can extend the control by using access control lists, ACL's  Requesting the ACL's on a directory will show us if "dfs.namenode.acls.enabled" is set to tru on HDFS: [root@linux-x64]# hdfs dfs -getfacl /user # file: /user # owner: hdfs # group: supergroup getfacl: The ACL operation has been rejected.  Support for ACLs has been disabled by setting dfs.namenode.acls.enabled to false. In...

Whenever we run a BDA upgrade we see as one of the prerequisites checks, to have the httpd service up and running on the first node of the cluster - The httpd service must be started on Node 1 of the cluster. It should be stopped on all other nodes. This is only needed during cluster upgrade or reconfiguration, but it is recommended to have it running at all times. The reason for that is because we will run yum from every node in the cluster pointing to the repository that is...

It may happen that when trying to reach the Exadata machine using the management network, the data center switch that connects to the Exadata Cisco switch get a 'connection rejected' error. On X7-2 port 48 of the Cisco switch is setup by default as ‘spanning tree network’ that set the BPDU* filter to disable, and communications between customer switch and the Cisco are rejected. To solve run this command on the Cisco: spanning tree BPDU filter en Enabling BPDU filtering in the...

Recently I had a BDA server that was refusing to come up. Every trial to run a start /SYS failed. We were able to identify this as a motherboard failure, then the motherboard was replaced and we were able to bring up the server using the ILOM. Back on track I've tried to setup the management network, but this failed because the eth0 NIC was missing. [root@bdanode01 ~]# ethtool -i eth0 Cannot get driver information: No such device But I've noticed we had eth1 available,...

Lately I had to help various customers to replace their old storage cells with the new X7-2 ones. There are huge benefits in doing this, the X7 has 25.5TB of flash, 12 x 10TB disks and 192 GB of DDR4 Memory.                       The question my customers asked the most was: Can we do the migration from our old storage to the new X7 without downtime and without risk? The answer was: YES! For doing this I've prepared and implemented a procedure that cover step by step how to migrate...

Setting passwordless ssh root connection using dcli is fast and simple and will easy later to execute commands on all servers using this utility. In order to do that you should have either: DNS resolution to all Database and Storage nodes OR have them registered in /etc/hosts 1) Create a parameter file that contains all the server names you want to reach via dcli, tipically we have a cell_group for storage cells, a dbs_group for database servers and an all_group for both of...

Complete information about the security fix availability should be reviewed, before applying the fix, in MOS DOC:  Responses to common Exadata security scan findings (Doc ID 1405320.1) The security fix is available for download from: http://public-yum.oracle.com/repo/OracleLinux/OL5/latest/x86_64/getPackage/bash-3.2-33.el5_11.4.x86_64.rpm The summary installation instructions are as follows: 1) Download getPackage/bash-3.2-33.el5_11.4.x86_64.rpm 2) Copy...

Exadata auto disk management is controlled by the parameter _AUTO_MANAGE_EXADATA_DISKS. The default value for this parameter is TRUE. When _AUTO_MANAGE_EXADATA_DISKS is enabled, Exadata automate the following disk operations: If a griddisk becomes unavailable/available, ASM will OFFLINE/ONLINE it. If a physicaldisk fails or its status change to predictive failure, for all griddisks built on it ASM will DROP FORCE the failed ones and DROP the ones with predictive failures.If a...

Sometimes I have heard that Exalogic is just a bunch of servers connected using infiniband, something that you can easily build yourself at a lower cost. That comments misses completely 2 things: 1) What is the idea behind an Oracle engineered system, and the back that Oracle provides for them  2) What is Exalogic This amazing 5 minute presentation explains Exalogic potential: Oracle Exalogic Elastic Cloud