Important Things 1999

Now, we can use disk as data backup media, so it appeared, the dedupe.

We think disk can be more available than tape, and it’s more suitable for random read and write I/O, and there is no need to mount tape and find record position. All of physical operations can be replace by disk header’s moving.

It’s funny.

Dedupe depends on the safety of the first backup data, if it lost for any reason, the hazard can not be evaluated.

To make sure the first data is available at any time, let’s look at what we can do.

First, we using RAID, most is RAID5, even RAID6. With hot spare disk, we can prevent data lost under two disks broken.

Second, Volume Mirror.

Third, data file can be splitted to blocks and stored in distribution storage, maybe it like the concept of cloud storage, which is prompted by EMC now.

Forth, multicopy over network.

Fifth, tape backup. Haaaaaaaaaaaaaaaaaaaaa, we return to the start point. Under most circumstance tape-backup is not the best choice comparing with disk-backup, but no one can discard it. If using this method, we assume disk dedupe will not lose data in most situation, if lose, whether it can be recovered, depends on our fortune or planning. If you have a careful design of tape-backup planning, such as shedule testing and recovery, dual copies in different sites, tape-backup is reliable. So why we still use dedupe?

Dedupe, using time to change space. We have powerful calculation, but limit disk space(more expensive than tape). To save space must consume CPU, alse using more CPU in recovery.

Another question, how long the method of dedupe can exist. Tape can be preserved in tens of year, but dedupe device? The deduped data must be re-stored or re-backuped in tapes at last, untill we found other mothed to replace tape.

by IT1999

at 1:00am, Feb. 19, 2009

IT1999: Want convert .chm to html? There is a free software named “CHM Decode” which is only 504KB, single .exe file. The following content is copied from http://gridinsoft.com/chm.php

CHM Decoder may decompile your CHM file (Compiled Windows HTML Help) or e-book and extract all source files. This tool free for use and work easily and quickly.

Step 1 – Press ‘Open’ and select CHM file

Step 2 – Press ‘Go!’ for decompile

Want you convert CHM to HTML and view that in your PocketPC or in your web pages? Try CHM Decoder now!

The program supports command line. Using batch mode, you can convert several documents simultaneously:

chmdecoder.exe [-menu] chm_file [destination_path]

Gmail begins to support offline function as google lab announced today.

To use offline Gmail, you must,

1. install google gear.

http://gears.google.com/

2. visit gmail lab tab URL, and enable offline option.

http://mail.google.com/mail/?ui=2&fs=1&view=pu&st=labs

I have pasted the two URLs above, if you want more details, please read following introduction copied from google, or visit : http://gmailblog.blogspot.com/2009/01/new-in-labs-offline-gmail.html

New in Labs: Offline Gmail

Tuesday, January 27, 2009 4:00 PM

Posted by Andy Palay, Gmail engineer

Web-based email is great because you can check it from any computer, but there’s one little catch: it’s inherently limited by your internet connection. From public WiFi to smartphones equipped with 3G, from mobile broadband cards to fledgling in-flight wireless on airplanes, Internet access is becoming more and more ubiquitous — but there are still times when you can’t access your webmail because of an unreliable or unavailable connection.

Today we’re starting to roll out an experimental feature in Gmail Labs that should help fill in those gaps: offline Gmail. So even if you’re offline, you can open your web browser, go to gmail.com, and get to your mail just like you’re used to.

Once you turn on this feature, Gmail uses Gears to download a local cache of your mail. As long as you’re connected to the network, that cache is synchronized with Gmail’s servers. When you lose your connection, Gmail automatically switches to offline mode, and uses the data stored on your computer’s hard drive instead of the information sent across the network. You can read messages, star and label them, and do all of the things you’re used to doing while reading your webmail online. Any messages you send while offline will be placed in your outbox and automatically sent the next time Gmail detects a connection. And if you’re on an unreliable or slow connection (like when you’re “borrowing” your neighbor’s wireless), you can choose to use “flaky connection mode,” which is somewhere in between: it uses the local cache as if you were disconnected, but still synchronizes your mail with the server in the background. Our goal is to provide nearly the same browser-based Gmail experience whether you’re using the data cached on your computer or talking directly to the server.”

Offline Gmail is still an early experimental feature, so don’t be surprised if you run into some kinks that haven’t been completely ironed out yet. We’ve been using offline Gmail internally at Google for quite a while (I’ve read thousands of messages and answered hundreds en route to visit my son and my daughter). And it’s saved me more than once when my home network connection ran into issues (we have squirrels at home that love to chew through outside cable wires). Now we’re ready to have a larger set of people try it out, so we’re making it available in Gmail Labs for those of you who want to test out Gmail’s latest and greatest and send us your feedback.

We’re making offline Gmail available to everyone who uses Gmail in US or UK English over the next couple of days, so if you don’t see it under the Labs tab yet, it should be there soon. Once you see it, just follow these steps to get started:

1. Click Settings and click the Labs tab.
2. Select Enable next to Offline Gmail.
3. Click Save Changes.
4. After your browser reloads, you’ll see a new “Offline^0.1” link in the upper righthand corner of your account, next to your username. Click this link to start the offline set up process and download Gears if you don’t already have it.

… …

More information, please visit: http://gmailblog.blogspot.com/2009/01/new-in-labs-offline-gmail.html, where also has a vedio introduction.

IT1999: Having discuzed a lot of software, maybe it’s time to change some other topics.

To know the architecture of other websites, or basic opration, or maintanance, the following information may be useful for a webmaster.

IT1999: There is no new ideas of architecture, only reconsidering cache, SLB(Server Load Balance) and network storage with the most cheapest solution. All of concepts existed early before 2001, the difference is now we have more choices, especially with open source codes, and there is no need to explain the concept of SLB and CDN any more. Unlike Sina.com.cn, Sohu.com, none of them use Alteon(Nortel now), F5, Radware, … as SLB device. So does caching device, most of  web 2.0 sites use open source application to cache images.

======================================

QCon San Francisco 2008: http://qconsf.com/sf2008/

Web 2.0 Summit 2008: http://en.oreilly.com/web2008/public/content/home

MySQL Conference & Expo 2008: http://en.oreilly.com/mysql2008/

More: http://conferences.oreillynet.com/

Others:

Wikimedia Architecture: http://highscalability.com/wikimedia-architecture

Youtube Scalability:

http://kylecordes.com/2007/07/12/youtube-scalability/

The following content is copied from above URL.

YouTube Scalability Talk

Cuong Do of YouTube / Google recently gave a Google Tech Talk on scalability.

I found it interesting in light of my own comments on YouTube’s 45 TB a while back.

Here are my notes from his talk, a mix of what he said and my commentary:

In the summer of 2006, they grew from 30 million pages per day to 100 million pages per day, in a 4 month period. (Wow! In most organizations, it takes nearly 4 months to pick out, order, install, and set up a few servers.)

YouTube uses Apache for FastCGI serving. (I wonder if things would have been easier for them had they chosen nginx, which is apparently wonderful for FastCGI and less problematic than Lighttpd)

YouTube is coded mostly in Python. Why? “Development speed critical”.

They use psyco, Python -> C compiler, and also C extensions, for performance critical work.

They use Lighttpd for serving the video itself, for a big improvement over Apache.

Each video hosted by a “mini cluster”, which is a set of machine with the same content. This is a simple way to provide headroom (slack), so that a machine can be taken down for maintenance (or can fail) without affecting users. It also provides a form of backup.

The most popular videos are on a CDN (Content Distribution Network) – they use external CDNs and well as Google’s CDN. Requests to their own machines are therefore tail-heavy (in the “Long Tail” sense), because the head codes to the CDN instead.

… …

Read more please click here to visit : http://kylecordes.com/2007/07/12/youtube-scalability/

Usually, I use VPN to update my Outlook. After succeed dial-up, the policy of company will prohibit you to visit lots of websites, such as youtube, google word, and all vicious websites he thinks. How to visit those websites and update Outlook at the same time?

This is my VPN solution:

1. Host OS: Ubuntu Linux
2. Guest OS: Microsoft Windows in VMware Workstation/Server for Linux(If you are VCP of VMware, they will send you a formal Workstation license after passing training class and VCP-310 test).
3.  CISCO VPN and Outlook software is installed in guest OS(Windows).
4. Using Linux to visit website which is prohibitted by the company’s firewall.
5. Using Windows to dial VPN, and setup VPN tunnal, Outlook will using this tunnal to receive and send email.

Since tunnel is setup by Windows, no Ubuntu, so Ubuntu can do anything without considering firewall of company. This will be helpful when you work at home.

Internet access network can be ethernet or wireless, because Windows(Virtual machine) don’t care about it, setup of physical line is job of Ubuntu.

If this article help you, I will be pleasure to hear from you.