But advocates of DC power continue to make the case for direct current distribution in data centers. The recent Data Center Efficiency Summit featured a case study showing gains over AC systems, and discussion of whether global efforts to establish a standard for 380 volt systems might build momentum for DC power.
via New Study Reinforces Case for DC Power Savings » Data Center Knowledge.
How do you list the network open ports on your server and the process that owns them? The answer is simple use the following command (must run as root):
sudo lsof -i
sudo netstat -lptu
via Linux List The Open Ports And The Process That Owns Them.
I don’t know why I keep forgetting this.
“Maintenance is a very lucrative business,” said Fairfax, who said guidance from equipment vendors sometimes slip into FUD (fear, uncertainty doubt) rather than sound methodology. “They want to keep selling their maintenance plans. To overcome this preventive maintenance threat, we must attack false learning. More is not always better.”
via Is Maintenance Making Your Facility Less Reliable? » Data Center Knowledge.
File this under don’t fix what ain’t broke.
The syntax for the rename command is:
rename [ -v ] [ -n ] [ -f ] perlexpr [ files ]
-v means “verbose” and it will output the names of the files when it renames them. It is a good idea to use this feature so you can keep track of what is being renamed. It is also a good idea to do a test run with -n which will do a test run where it won’t rename any files, but will show you a list of files that would be renamed.
via How to Bulk Rename Files in Linux (Terminal or GUI) | Webmaster Tips.
A5/1 is a stream cipher used to provide over-the-air communication privacy in the GSM cellular telephone standard. It was initially kept secret, but became public knowledge through leaks and reverse engineering. A number of serious weaknesses in the cipher have been identified.
scanning for new scsi devices.
New devices can be added using echo “scsi add-single-device <h> <b> <t> <l>” > /proc/scsi/scsi where the variables are host, bus (channel), target (scsi id) and lun. The success (or otherwise) of this command can be determined by sending a subsequent cat /proc/scsi/scsi command.
..from the scsi-howto (proc interface) at www.tldp.org – see it for more info.
i have a script “rescan-scsi-bus.sh” here on debian which uses the above method to recheck devices.
HTH ritch.
This was written in 2005. I found the rescan-scsi-bus.sh script on medusa but have no idea which package it came from. It wasn’t on any other Fedora 14 install so it must have come from somewhere. It scans the SCSI bus and finds the drive perfectly well.
Symmetric multiprocessing – Wikipedia, the free encyclopedia.
In computing, symmetric multiprocessing (SMP) involves a multiprocessor computer hardware architecture where two or more identical processors are connected to a single shared main memory and are controlled by a single OS instance. Most common multiprocessor systems today use an SMP architecture. In the case of multi-core processors, the SMP architecture applies to the cores, treating them as separate processors. Processors may be interconnected using buses, crossbar switches or on-chip mesh networks. The bottleneck in the scalability of SMP using buses or crossbar switches is the bandwidth and power consumption of the interconnect among the various processors, the memory, and the disk arrays. Mesh architectures avoid these bottlenecks, and provide nearly linear scalability to much higher processor counts at the sacrifice of programmability:
The New Number One
The K Computer, built by Fujitsu, currently combines 68544 SPARC64 VIIIfx CPUs, each with eight cores, for a total of 548,352 cores—almost twice as many as any other system in the TOP500. The K Computer is also more powerful than the next five systems on the list combined.
Here is another article about this.
Computer cluster – Wikipedia, the free encyclopedia.
A computer cluster is a group of linked computers, working together closely thus in many respects forming a single computer. The components of a cluster are commonly, but not always, connected to each other through fast local area networks. Clusters are usually deployed to improve performance and availability over that of a single computer, while typically being much more cost-effective than single computers of comparable speed or availability.[1]
And now I will put together clusters for high availability and load balancing. This is where VMs come in handy. I think I prefer loosely coupled clusters, clusters where individual nodes are separated on different power grids.
It’s always nice to have a succinct definition handy to stay focused.