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Thu Jun 30 11:18:51 HKT 2016

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Thu Jul 21 19:29:09 HKT 2016 From /weblog/design/distribute


There are two key primary ways of scaling web applications which is in practice today.
1) “Vertical Scalability” - Adding resource within the same logical unit to increase capacity. An example of this would be to add CPUs to an existing server, or expanding storage by adding hard drive on an existing RAID/SAN storage.
2) “Horizontal Scalability” - Adding multiple logical units of resources and making them work as a single unit. Most clustering solutions, distributed file systems, load-balancers help you with horizontal scalability.

Scalability can be further sub-classified based on the “scalability factor”.
1) If the scalability factor stays constant as you scale. This is called “linear scalability“.
2) But chances are that some components may not scale as well as others. A scalability factor below 1.0 is called “sub-linear scalability“.
3) Though rare, its possible to get better performance (scalability factor) just by adding more components (i/o across multiple disk spindles in a RAID gets better with more spindles). This is called “supra-linear scalability“.
4) If the application is not designed for scalability, its possible that things can actually get worse as it scales. This is called “negative scalability“.

Report of building web application with 55k pageload with rail -[..]mongrels-handled-a-550k-pageview-digging

XMPP a IM protocol about scalability -[..]icle/the_aol_xmpp_scalability_challenge/

Presentation and resources of making you website more scalable -[..]9/Real-World-Web-Performance-Scalability[..]lications&asrc=EM_NLN_3990118&uid=703565[..]ionsPart2&asrc=EM_NLN_3990119&uid=703565

Brian Zimmer, architect at travel startup Yapta, highlights some worst practices jeopardizing the growth and scalability of a system:
* The Golden Hammer. Forcing a particular technology to work in ways it was not intended is sometimes counter-productive. Using a database to store key-value pairs is one example. Another example is using threads to program for concurrency.
* Resource Abuse. Manage the availability of shared resources because when they fail, by definition, their failure is experienced pervasively rather than in isolation. For example, connection management to the database through a thread pool.
* Big Ball of Mud. Failure to manage dependencies inhibits agility and scalability.
* Everything or Something. In both code and application dependency management, the worst practice is not understanding the relationships and formulating a model to facilitate their management. Failure to enforce diligent control is a contributing scalability inhibiter.
* Forgetting to check the time. To properly scale a system it is imperative to manage the time alloted for requests to be handled.
* Hero Pattern. One popular solution to the operation issue is a Hero who can and often will manage the bulk of the operational needs. For a large system of many components this approach does not scale, yet it is one of the most frequently-deployed solutions.
* Not automating. A system too dependent on human intervention, frequently the result of having a Hero, is dangerously exposed to issues of reproducibility and hit-by-a-bus syndrome.
* Monitoring. Monitoring, like testing, is often one of the first items sacrificed when time is tight.

Useful Corporate Blogs that Talk About Scalability -[..]l-corporate-blogs-talk-about-scalability

Overview of mapreduce and how it compare with other distributed programming model -[..]0/is-mapreduce-going-to-main-stream.html

Paper of data store at amazon

Discuss how haven't sync can cause performance issue -[..]lications&asrc=EM_NLN_6273194&uid=703565

Discussion about Cloud Based Memory Architectures -[..]ased-memory-architectures-next-big-thing[..]alability-and-performance-best-practices

Interview with google engineer -[..]gle-at-scale-everything-breaks-40093061/

Surprisingly youtube is blocking -[..]e-scalability-lessons-in-30-minutes.html

If we are seeing a sustained arrival rate of requests, greater than our system is capable of processing, then something has to give. Having the entire system degrade is not the ideal service we want to give our customers. A better approach would be to process transactions at our systems maximum possible throughput rate, while maintaining a good response time, and rejecting requests above this arrival rate. -[..]apply-back-pressure-when-overloaded.html

How twitter scaling -

How Reddit scaling -

How Hotjar scaling -[..]-while-scaling-hotjars-tech-architecture

How infiniteDB prevent locking and IO -[..]-scalable-relational-database-manag.html[..]ard-way-about-scaling-a-million-use.html[..]2014/03/26/six-things-about-scaling.html

The experiences of various big companies, about network issues -

Stackoverflow, scale without cloud -[..]nth-25-servers-and-i.html?SSLoginOk=true

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Mon Jul 18 00:08:29 HKT 2016 From /christianity


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Sat Jul 16 11:23:51 HKT 2016 From /weblog/science


psychology-tells-you-about-yourself -[..]ology-tells-you-about-yourself/?view=all

body-hacks-life-is-trying-to-hide-from-you -[..]ife-is-trying-to-hide-from-you/?view=all

causes-dark-circles-eyes-sleeping-people-really-tired -[..]s-sleeping-people-really-tired/?view=all

facts-about-the-human-body-you-may-not-be-aware-of -[..]n-body-you-may-not-be-aware-of/?view=all

blood -[..]you-might-not-know-about-blood/?view=all

misconceptions-about-your-body -[..]bout-your-body-that-arent-true/?view=all

pregnancy -[..]nge-the-way-you-view-pregnancy/?view=all

blindness -[..]you-didnt-know-about-blindness/?view=all

【趣味科普】同理心等於同情心?可以後天鍛鍊嗎? -[..]om/realtime/supplement/20160712/55345201

happen-to-your-body-after-you-die -[..]pen-to-your-body-after-you-die/?view=all

your-body-is-weirder-than-you-think -[..]body-is-weirder-than-you-think/?view=all[..]-that-make-absolutely-no-sense/?view=all

DNA -[..]l-help-you-understand-yourself/?view=all[..]-genetics-and-the-human-genome/?view=all

「人體農場」:聽屍體說話 -[..]%BD%E5%B1%8D%E9%AB%94%E8%AA%AA%E8%A9%B1/[..]8%82%89%E9%AA%A8%E6%9F%A5-q-a-episode-4/

Lie/Cheat -[..]o-know-someone-is-lying-to-you/?view=all

Albinism -

人腦越來越小 又關facebook事? -[..]om/realtime/supplement/20160705/55315802

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Sat Jul 16 11:20:49 HKT 2016 From /weblog/learning


How to learn language in 30 days -[..][..]power-of-daily-positive-words-15115.html

Language make the difference -[..]shocked-by-chinese-multiplication-table/

crazy-facts-about-languages -[..]nguage-fluently-quickly-and-efficiently/

5 tips for learning Mandarin -[..]-great-advice-from-a-variety-of-experts/

Resource of learning a lot difference languages -

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Wed Jul 13 16:54:33 HKT 2016 From /weblog/unix


A very nice sectioned list of unix command -

Backup a list of directories -

A quick reference -

Tuning cheat sheet -

Common and difference between systems -

BSD for linux user -

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Wed Jul 13 10:39:49 HKT 2016 From /weblog/career


First, don't lie at the CV....

Some useful information from the thread:
online learning listing:
uk university listing:

The other useful resource of writing CV,1217,a=182353,00.asp

Number 1: The overblown objective
Number 2: The poorly executed bluff
Number 3: The mug shot
Number 4: The block party
Number 5: Wallflower skills[..]/Avoid%20these%20five%20resume%20killers

"Edit your resume so it sounds like you are talking to someone." -[..]3/four-tips-for-defining-your-value.html

It look like tips for writing cover letter, but maybe good to include in customized CV also -

How boss spend 6 seconds to read your CV -[..]%A0%E7%9A%84%E5%B1%A5%E6%AD%B7%E8%A1%A8/

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Tue Jul 12 12:02:07 HKT 2016 From /weblog/database/sql


How to do limit resultset correctly -[..]ination-with-your-in-house-db-framework/

Using function result as table -[..]7/07/postgresqls-table-valued-functions/

Sample of using pivot -[..]/are-you-using-sql-pivot-yet-you-should/ and unpivot -[..]ess-your-coworkers-by-using-sql-unpivot/

Sample of using intersect -[..]the-underestimated-two-way-in-predicate/

Using temp table, rownum, and CTE -[..]licate-rows-from-table-SQL-database.html[..]log/2016/07/07/a-beginners-guide-to-sql/

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Mon Jul 11 14:54:49 HKT 2016 From /gallery/Home/YimKan/whatapp


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Tue Jul 05 16:29:21 HKT 2016 From /weblog/java/concurrency


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Tue Jul 05 15:09:28 HKT 2016 From /weblog/trip


May not really useful

【飲食男女】飛機中伏位|走廊多菌 座位要識揀 -
【飲食男女】飛機中伏位|摺枱加料 尿片飛機餐 -
【飲食男女】飛機中伏位|飛機餐陳年生果 小心為上 -

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Sat Jul 02 23:40:03 HKT 2016 From /weblog/languages


Prevent NPE from scala -[..]es-virginia-scala-can-save-you-from.html

Map scala function to java -[..]rarajan/entry/scala_for_java_programmers
Examples to show good points of Scala -

Var and Val -

Pattern in scala -[..]d/sites/default/files/FrederikThesis.pdf

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Thu Jun 30 21:56:43 HKT 2016 From /weblog/computer+science


John Von Neumann -[..]012/12/john-von-neumann-documentary.html

Bill Gate -[..]/interesting-facts-about-bill-gates.html

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Thu Jun 30 11:30:07 HKT 2016 From /weblog/hardware


Memory Ordering in Modern Microprocessors -[..]ors/25-microchips-that-shook-the-world/0

FPGA CPUs, how to turn a FPGA to a working CPU? -[..]com_myblog&show=FPGA-CPUs.html&Itemid=29

If according this article, GPU easier to have more cores is required code to be very regular fashion with no branches and inter-thread communication -

CPU DB: Recording Microprocessor History -

Difference CPU comparing -[..]12/03/28/fractal-and-crypto-performance/

Detail about how CPU caching work -[..]/2013/02/cpu-cache-flushing-fallacy.html

CPU design on paper -[..]0_h&elq=891e5022435b400e89040e1342c10b72[..]rdware-transactional-memory-in-java.html

Interview about TSX -[..]views/tene-hardware-transactional-memory

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Thu Jun 30 11:21:18 HKT 2016 From /weblog/hardware


Discuss at SDD about performance characteristic and reliablity -

SSD and Log file system -[..]ragged-windows-8-optimize-defragment-ssd[..]rt-1-introduction-and-table-of-contents/[..]uth-about-mapreduce-performance-on-ssds/

设计SSD友好的应用 -

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Wed Jun 29 09:00:44 HKT 2016 From /weblog/photographic


星軌拍攝技巧 數問 -

1).數碼機因hot pixel而唔適合曝得耐...最好分開影影夠幾個鐘...咁每張間隔之間都要俾CMOS斗下氣?
有師兄 教過 分十幾張 每張 10-20min 再合成 好過 一野 暴 幾粒鐘, (菲林 令計)

2).數碼機有D人話用ISO 100、有人話用ISO 400-800好...如果用合成方法...其實係咪都係就番光害而定...定係關雜訊事?
睇天氣 , 小弟 用 o個次 用 iso 100

4季 都唔同 位置, 用星座 搵 會準確 d, e+ 係 冬季, 北極星 位置 係 獵戶座 (lei 個最易 認, 唔會 搵唔倒 ... ) 頭頂 (腰帶 致 頭頂 距離 再過 5倍左右)

附圖 係 舊年 去雲南 香格里拉 時影, 本泥想 長暴, 不過 o個晚 太涷 個人 頂唔順 要收皮 反酒店

With a lot of information, 香港的星空 — 觀測及拍攝資訊 -

Herman's articles at dcfever -

500px tutorial -

About Comet -

Atmospheric optical phenomena 大氣光學現象 -[..]16/06/atmospheric-optical-phenomena.html

這張是11月15日凌晨拍攝的M42獵戶座星雲, 大埔的光害較嚴重, 所以要加上IDAS V4濾鏡作長時間曝光, 分三段不同時間曝光及作Layer Masking 處理, 把動態範圍拉闊. 在月光的影下算是滿意, 希望之後可以分數晚作10小時以上的曝光並加長每一張frame 的曝光時間 (現在是5分鐘一張), 使到暗位的表現進一步改善.

Place: Tai Po
Date: 14 Nov, 2013 (UT)
Camera: Canon 20Da
Lens: Canon EF-600 F4L
Mount: Vixen Sphinx with Star Book
Filter: IDAS V4
Exposure: 10 sec x 10, 30 sec x 10, 300sec x 26
ISO: 800
Guiding: Borg 60mm telescope, AIS120MM, PHD guiding.
Image calibration: Dark x 20 (average) for each exposure, Bias x 16 (Median), Dark subtracted Flat field x 20 (Median)
Processing: DSS, PS: layer Mask, Cropped, curve, colour adjusted.

how-to-find-the-milky-way -[..]om/2015/07/24/how-to-find-the-milky-way/

how-to-capture-sharp-star-photographs -[..]10/how-to-capture-sharp-star-photographs

銀河 - 觀測和拍攝 -

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Mon Jun 27 14:21:19 HKT 2016 From /gallery/Home/YimKan/whatapp


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Sun Jun 26 21:07:19 HKT 2016 From /gallery/Home/YimKan/whatapp


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Sun Jun 26 21:07:06 HKT 2016 From /gallery/Home/YimKan/whatapp


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Sat Jun 25 07:22:00 HKT 2016 From /gallery/Home/YimKan/whatapp


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Sat Jun 25 07:12:15 HKT 2016 From /gallery/Home/YimKan/whatapp


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Fri Jun 24 13:13:13 HKT 2016 From /gallery/Home/YimKan/whatapp


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Thu Jun 23 21:28:57 HKT 2016 From /gallery/Home/YimKan/whatapp


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