Primary keys are not enforce by Redshift. Must be enforced by the application:
Friday, May 17, 2013
Oracle ADDM monitoring on AWS
OEM 12c is the away to go for monitoring ADDM metric (DB diagnostic for ADDM). You can test drive OEM 12c running on AWS EC2 here:
You can also monitor EC2, RDS and EBS volumes when running Oracle on AWS using the OEM 12c plug-in for AWS:
Wednesday, May 15, 2013
Oracle DirectNFS
OracleDirectNFS (DNFS) is used mostly for cloning dev and test on Oracle. This is great post here:
This has not be tested on EC2/EBS but should work fine. I would not use for production.
EC2 instances life cycle
Here is a mapping of server hardware lifecycle to AWS EC2:
1. Start : On AWS - ec2-start-instances
Note: This is different then instantiating an instance for the the first time (from an AMI). The command for this is ec2-run-instances.
2. Reboot : On AWS - ec2-reboot-instances
(If a Linux/UNIX instance does not cleanly shut down within four minutes, Amazon EC2 will perform a hard reboot)
Note: Instance reboots are reboots of your virtual instance, and are equivalent to an operating system reboot. You can also reboot your instance from the operating system of your instance. More here: http://serverfault.com/questions/350581/differences-between-reboot-and-ec2-reboot-instances
3. Hard kill : ec2-stop-instances
4.AWS option : ec2-terminate-instances http://docs.aws.amazon.com/AWSEC2/latest/CommandLineReference/ApiReference-cmd-TerminateInstances.html
Note: This would be like throwing away a machine but keeping the hard drive.
Tagging instances can be done at anytime using the ec2-create-tags command.
EC2 (classic) instance hostname is not hostname and is not hostname
This is the results from wget and hostname at command line.
1. wget -q -O - http://169.254.169.254/latest/meta-data/public-hostname
Output ---> ec2-50-13-20-1.compute-1.amazonaws.com
2. wget -q -O - http://169.254.169.254/latest/meta-data/hostname
Output--> ip-10-222-1-241.ec2.internal
3. wget -q -O - http://169.254.169.254/latest/meta-data/local-hostname
output--->ip-10-222-1-241.ec2.internal
4. wget -q -O - http://169.254.169.254/latest/meta-data/local-ipv4
output--->10.222.1.241
5. wget -q -O - http://169.254.169.254/latest/meta-data/public-ipv4
50.13.20.1
6. [root@wls1 ~]# hostname ---> linux command line
wls1.labs.oracleweblogic.com
Someone changed the host name after boot or at boot time using user-data or another method. Normally you would see:
1. wget -q -O - http://169.254.169.254/latest/meta-data/hostname
Output ---> ip-14-222-22-28.us-west-2.compute.internal
2. hostname: hostname ---> linux command line
ip-14-222-22-28
AWS VPC public and private subnets
What is the difference between a private and public subnet? I asked myself this after I was looking for a field in the ec2-describe-subnets command, AWS console, and ElasticWolf, and could not find anything to indicated whether a subnet was private or public...
Public and private subnets are more or less the same thing. The routing table will decide whether a subnet is public or private. A subnet with a default route to the Internet Gateway, and instances using Elastic IPs, is considered as public. If you remove the Internet Gateway, you now have a private subnet.
This means that instances in a private subnet are invisible to the outside world and don't have access to the outside world (i.e internet). Therefore, instances in private subnets need to make use of a NAT instance. The NAT instance will basically accept all traffic coming from the private instances and send it out to the Internet Gateway. That would theoretically add some latency.
Back to my original question: So, if an IGW is associated with your subnet it is a public subnet.
Public and private subnets are more or less the same thing. The routing table will decide whether a subnet is public or private. A subnet with a default route to the Internet Gateway, and instances using Elastic IPs, is considered as public. If you remove the Internet Gateway, you now have a private subnet.
This means that instances in a private subnet are invisible to the outside world and don't have access to the outside world (i.e internet). Therefore, instances in private subnets need to make use of a NAT instance. The NAT instance will basically accept all traffic coming from the private instances and send it out to the Internet Gateway. That would theoretically add some latency.
Back to my original question: So, if an IGW is associated with your subnet it is a public subnet.
Monday, May 13, 2013
Distributed File System : Network, Distributed or Clustered ?
I often times hear these three distinct DFSs used to mean one in the same. This presentation does a nice job of describe how they are different and how they are the same:
http://lvee.org/uploads/image_upload/file/273/savchenko-distributed-fs.pdf
Network File System: A single server (or at least an appearance) and multiple network clients.
Examples: NFS, CIFS
Clustered File System:Servers sharing the same local storage (usually SAN at block level)shared storage architecture.
Examples: GFS2, OCFS2
Distributed file system : “Shared nothing” model, independent servers. intelligent server architecture.
Examples: pNFS, AFS
http://lvee.org/uploads/image_upload/file/273/savchenko-distributed-fs.pdf
Network File System: A single server (or at least an appearance) and multiple network clients.
Examples: NFS, CIFS
Clustered File System:Servers sharing the same local storage (usually SAN at block level)shared storage architecture.
Examples: GFS2, OCFS2
Distributed file system : “Shared nothing” model, independent servers. intelligent server architecture.
Examples: pNFS, AFS
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