ppadala - Slashdot User

Submission + - AT&T's U-verse: Want TV over phone lines ?

Submitted by

ppadala

on Sunday May 27, 2007 @03:36PM

ppadala writes: "AT&T is upgrading their phone lines to offer video programmes over phone line. The service, which will be available in parts of southern California communities initially, is similar to your cable and dish offerings. AT&T is insisting that,

This offering is on par with those of its cable rivals. But AT&T claims that it offers customers more for their money, including fast channel changing, video-on-demand, three set-top boxes, a digital video recorder, a picture-in-picture feature that allows viewers to surf channels without switching channels and an interactive program guide.
"

Submission + - Bye bye Spam and Phishing with DKIM?

Submitted by

ppadala

on Thursday May 24, 2007 @05:34PM

ppadala writes: "While research from PEW Internet (PDF) shows that few users really are bothered by spam, IETF is supporting a public key cryptographic based e-mail authentication mechanism called DomainKeys Identified Mail (DKIM) Signatures . The new spec is supposed to help in fighting both spam and fraud. From Ars Technica,

DKIM's precursor, DomainKeys, was originally developed by Yahoo. The specifications for DKIM were then extended by an informal group of IT organizations that included companies like Yahoo, Cisco, EarthLink, Microsoft, and VeriSign, among others. It was first submitted by the group to the IETF in mid-2005, but only recently published by the IETF. The spec is still to be incorporated into a more formal draft and submitted for approval, however.
"

Submission + - Experience uber search with Google

Submitted by

ppadala

on Wednesday May 16, 2007 @07:23PM

ppadala writes: "Google today unveiled its "uber search" which allows you to search for text, images, news etc. together. This is the result of unifying various search engines that Google developed for web, images, news etc. PCWorld has an article describing the new universal interface. Google's main page and the results page are also sporting a polished look with a top menu bar sporting various search items."

Comment Re:comparing apples to orange (Score 1) 116

by ppadala on Tuesday May 15, 2007 @12:54PM (#19132483) Attached to: Performance Evaluation of Xen Vs. OpenVZ

The article (yup, I've speed read TFA) defines Xen as a para-virtualization systems... Completely ignoring that since now years Xen also allows to do hardware-virtualization. Another posted also noted already that Xen's power lies in its ability to run different OSes.

Btw I happen to run my Samba / NFS / CVS / SVN server on a Xen para-virtualized domU. For hardware-virtualization I tried Xen too and the open, free, version lacks good I/O drivers for Windows (slow network and slow disk).

We very well know that Xen supports hardware-virtualization as well. As you pointed out, the performance is abysmal because Xen still uses IO emulation while using hardware virtualization.

People want to Google on exactly "Which virtualization is right for you" and read infos from a knowledgable sysadmin (managing thousands of servers and virtual servers on a lot of various platforms and, no, it's not me) instead of an article performing micro-benchmarking of hypercalls to compare apples to oranges.

These are NOT micro-benchmarks. Infact, I would call them macro benchmarks. A few server consolidation scenarios are setup and the performance of Xen and OpenVZ is compared. Then, we dug deeper to find out the reasons for the problems using Oprofile. It's not comparing orranges to apples, because both technologies are touted for server consolidation.

There's no single virtualization technology that works for every one, as many have explained in earlier comments.

Pradeep

Submission + - Xen vs. OpenVZ - a performance evaulation

Submitted by Anonymous Coward on Monday May 14, 2007 @08:19PM

An anonymous reader writes: Xen is a hypervisor level virtualization technology that allows multiple operating systems to be run with and with out para-virtualization. OpenVZ is an operating system level virtualization technology that allows creation of virtual environments similar to virtual machines that are more powerful than traditional jails. Though OpenVZ does not allow running multiple operating systems, the gain in performance due to running virtual containers in a single operating system kernel is very appealing. Xen trades off performance for much better isolation and security. How big is the trade-off ? A performance evaluation study done by researchers at the University of Michigan and HP labs provides insight into the cause of overheads (primarily L2 cache misses). From the tech report,

... We compare both technologies with a base system in terms of application performance, resource consumption, scalability, low-level system metrics like cache misses and virtualization-specific metrics like Domain-0 consumption in Xen. Our experiments indicate that the average response time can increase by over 400% in Xen and only a modest 100% in OpenVZ as the number of application instances grows from one to four. This large discrepancy is caused by the higher virtualization overhead in Xen, which is likely due to higher L2 cache misses and misses per instruction. A similar trend is observed in CPU consumptions of virtual containers. We present an overhead analysis with kernel-symbol-specific information generated by Oprofile

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