Monday, September 3, 2007

Viability of DNS failover

In Spring 2006, my site was plagued with recurrent hardware problems causing serious downtime. At the time, the site was hosted on a dedicated server and I had no failover strategy whatsoever so when a hard disk failed on the server, you could expect a few days of downtime.

At the beginning of the summer, I got fed up and started investigating possible solutions to this problem and, after some experimentation, finally settled on DNS failover. Here are the results of the experimentation, originally posted on WebHosting Talk:

I run a site with about 1,000,000 unique visitors per month and recent server failures made me decide to get a failover server to minimize downtime. My goal wasn't to get 99.999% uptime but to be able to be back on track after a failure in a "reasonable" amount of time. After evaluating several solutions, I decided to go with DNS failover. Here's how the setup work:

1) mydomain.com points to main server with a very low TTL (time to live)
2) failover server replicates data from main server
3) when main server goes down, mydomain.com is changed to point to failover server

The drawback is the DNS propagation time since some DNS servers don't honor the TTL and there is some caching happening on the user's machine and browser. I looked for empirical data to gauge the extent of the problem but couldn't find any so I decided to setup my own experiment:

I start with mydomain.com pointing to the main server with a TTL of 1800 seconds (1/2 hour). I then change it to point to the failover server which simply port forwards to the main server. On the main server, I periodically compute the percentage of requests coming from the failover server which gives me the percentage of people for which the DNS change has propagated.

I made the DNS change at exactly 16:04 on 06/21/06 and here are the percentage of propagated users:

06/21/06 16:00 0 %
06/21/06 16:05 3 %
06/21/06 16:10 20 %
06/21/06 16:15 37 %
06/21/06 16:20 59 %
06/21/06 16:25 69 %
06/21/06 16:30 76 %
06/21/06 16:35 80 %
06/21/06 16:40 86 %
06/21/06 16:45 90 %
06/21/06 16:50 91 %
06/21/06 16:55 92 %
06/21/06 17:00 93 %
06/21/06 17:05 94 %
06/21/06 17:10 94 %
06/21/06 17:15 95 %
06/21/06 17:35 95 %
06/21/06 17:40 96 %
06/21/06 17:45 97 %
...
06/22/06 10:40 99 %

So even after 18 hours, there is still a certain percentage of users going to the old server so DNS failover is obviously not a 99.999% uptime solution. However, since more than 90% of the users are propagated in the first hour, the solution works well enough for me.

1,230 comments:

«Oldest   ‹Older   1201 – 1230 of 1230
arohipatel said...

Our Call Girls Ahmedabad comes within the modest rates, though, we offer premium grade services.It is even hard to assume that you will make a similar experience, dealing with the mediocre grade agencies for Call Girls Ahmedabad.


http://follr.me/arohipatel/about ##
https://fontlibrary.org/en/member/arohipatel ##
https://www.fontshop.com/people/arohi-patel ##
https://www.forexfactory.com/arohipatel ##
http://forum.astro-galaxy.com/index.php?action=profile;u=14692 ##

riyachennai said...


Escort agencies do not just hire anyone and everyone to do the job. The Chennai escorts have to go through a process of intense examination for to pass out and join the agency.Easy and you have to go through some tiresome and scrutinous process to make that happen. visit my website:-
escorts in boat club road ##
escorts in poes garden ##
escorts in taramani ##
escorts in gopalapuram ##
escorts in velachery ##
escorts in anna salai ##
escorts in mylapore ##
escorts in koyambedu ##
escorts in adyar ##

Yami in Mumbai said...

Seductive services are best given by a sensuous Maharashtrian Escort in Mumbai! You can simply tell that Yami is a fun-loving elite companion! The way that she's bisexual is only a little look into the sort of things she gets up to! Join this with the exceptionally sensual services she gives and you have one overwhelming bundle! The attractive Maharashtrian sensuous exceeds expectations with regards to romantic services, for example, GFE. Consolidate this with a date out in the city and you'll be made to feel extremely glad to be sure. http://yamiinmumbai.in/
http://www.dianainmumbai.com/

Yami in Mumbai said...

There's no requirement to be lonely when this petite Maharashtrian is around. A pretty and petite Maharashtrian Escort in Mumbai, Diana is the liberal young lady you've been longing for. And so on, she does it. From watersports to subjugation, celebrating in clubs to appreciating a calm night in, you can make certain that she will be available! Situated in Bandra, the young elite girl is accessible for both outcalls and incalls in and around Mumbai. Believe us when we say that Diana will be booked quick! Simply ensure it's for you! http://www.dianainmumbai.com/

Yami in Mumbai said...

Do you need your BDSM young girl to be devious or nice? The BDSM young Pune Call Girl you had always wanted, Isa is accessible to be your easygoing or dominant escort! Understood for her amazing characteristic excellence, the sweet brunette has a naughty side that influences her ideal of servitude and unusual to roleplay! She may have a petite body yet she can do some huge things with it. From sexy OWO to sensual back rub, Jenny offers you an extensive variety of alternatives. In that capacity, you can pick what gives you the most joy! http://www.punecityescort.com/

Yami in Mumbai said...

Hey, my name is Jenny, I give VIP Escort Services in Pune. I'm brimming regarding others, kind, better than average, young lady, yet experienced, accessible for outcall all over Pune, I give, supper dates, just as spending awesome time at your flat or hotel and satisfy your wants. I'm true however fun-loving, kind and better than average, yet splendid and brimming with vitality, I' am certain we will fraternize, I have a beguiling grin, slim body, busty model that you will always remember! I'll come with the brilliant grin all over, I'm not an exhausting young lady and ready to make you extremely glad! I'm amiable, don't hesitate to discuss any subjects with me. http://www.jennyinpune.in/

Yami in Mumbai said...

A Nashik Call Girl could fulfill you extremely indeed! It's nothing unexpected to hear how cheerful Ayesha could make you. The Nashik Escort is a flirtatious young lady who completely conveys after her perky prodding. This excellent blonde darling is situated in Prem Nagar for incall bookings, however, she likewise adores appreciating outcalls in the city. Wherever you go, ensure you put some private time aside with the goal that Ayesha can flaunt that magnificent body of hers!
http://www.nashikescorts.in/
http://www.susanescorts.in/
http://appleescorts.com/
http://www.cherryescorts.in/

Gauri Sen said...

This is the reason they are also Known As Escorts In Aerocity. No other professional escorts have better skills and expertise to do their job. You just need to spend time with these call girls to feel their awesome and sensuous touch properly.

👉 vaishali escorts
👉 indirapuram escorts
👉 crossings republik escorts
👉 kaushambi escorts
👉 vasundhara escorts
👉 munirka escorts
👉 golf link escorts
👉 green park escorts
👉 uttam nagar escorts
👉 tilak nagar escorts

ishabajaj said...

chennai Escorts - Call Girls 24/7

chennai Escorts is the top preeminent Escort agency in where you can find high-class Call Girls in chennai who are independently available for you.

Click : - ☺☺☺☺☺☺☺☺☺☺☺☺☺☺☺☺☺☺☺☺

t nagar escorts #
velachery escorts #
guindy escorts #
adambakkam escorts #
mylapore escorts #

spaking said...

http://www.malikescorts.com/call-girls-agra/
http://www.malikescorts.com/category/sexy-call-girls/
https://www.escortsbulletin.com/agra.html
https://www.lailaescorts.com/agra.html
https://www.sexygirlscontact.com/agra/call-girls-agra.php
https://www.taniasharma.in/agra.php
https://www.taniasharma.in/callgirls-agra.php
http://www.blueheavenescorts.in/call-girls-available-ahmedabad-gujrat/
http://www.blueheavenescorts.in/call-girls-in-ahmedabad/
http://www.callgirlsbooking.com/call-girls-ahmedabad/

Mehak Aggarwal said...

Dehradun Escorts- 1Escorts- Are you looking for best Call girls in Dehradun at affrodable rate keep in touch with *Dehradun Escort.

Dehradun escorts

Dehradun escort service

call girls in dehradun

Mussoorie escorts

haridwar escorts

Rishikesh escorts

Source:- https://www.1escorts.club/

Sweety Khan said...

There many places in Hauz Khas which is famous for their escort service and Hauz Khas are one of them. The reason for the escort service in Hauz Khas to be so famous is because the call girls are the best at what they do and they put customer satisfaction before everything else.

👉 https://www.blurb.com/user/sweetykhan01?profile
👉 https://giphy.com/gifs/hauz-khas-escort-escorts-TiPW0Q8XERYvXcccPD
👉 https://www.ranker.com/writer/sweetykhan01
👉 https://speakerdeck.com/sweetykhan01
👉 https://new.internetpolyglot.com/user/399980
👉 Hauz Khas escort

krprince said...

Bangalore escort services

I respect myself, my decision and a man I am going to be with, will be my choice till the rest of my life. I am looking for a man who is ready to settle down and ready to take such an important decision as marriage, a man who is confident enough fort his life settlement because marriage is not a small decision but it’s our life. A kind, honest, caring and loving heart can build a happy family but a small misunderstanding and weakness can completely destroy a family. And I would prefer a strong and understanding man to take this life decision seriously as Bangalore escorts.

I think it is important to mention this from the beginning, and about me. I am a healthy woman with creative nature, who will wait for you after work with a caring, warm heart and tasty dinner. What can be more pleasant than this? May be seeing my husband standing on the threshold with a bouquet of roses. We would not even talk to any stranger if we don’t know them and here people are doing marriage with someone they have met only once or twice. That's ridiculous.

More about me, I am a fun loving girl who easily connects with everyone. I am looking for a partner with whom I can hang out and can get to know each other as Bangalore escort agency. Well, I am looking for a long term relationship it's not necessary but I want to go for a serious relationship. I can and I will make time for the right person.

I can’t even express how happy I am to be a wonder mother and respectful woman. If you are interested in a serious relationship, I am ready, I have taken my decision to start a family. I am sensual, aggressive in bed and unique. An exotic Bangalore call girl who loves her clients and who always wants to give everyone the maximum pleasure. An orgasm hunter, the mayor of the city of sex, a woman with many faces: lover, girlfriend, luxury Bangalore Independent Escorts, passive slave, porn star of your imagination.

I am a graceful and sensual lady escort offering a charming blend of intellect and humour, warm and playful, with sweet and brave spirit, who like to receive and offer pleasure. I am available for session of many different kind and duration. I live for excitement and the thrill of the new fantasies. Don't wait any longer to start an adventure with me however long or brief it may be my pleasure to make you happy with my escort skills.

I have a long list of escort services and happily offer you without a rush. My easy going personality will make you feel comfortable with showing my your wild side later. I am your ultimate  girl escort. You can request specific styles or outfits if you have something in particular that you like to see your escort in when you take them out. All you need to do is make these clear to me when you are fixing an appointment with Bangalore escort services.

Puneservice said...

Pune Escorts

Pune Escorts Services

Pune Call girls
Call girls in Pune
Pune Escort
Independent Pune Escorts Services

Pune Escorts Services
Pune Escorts
Escorts in Pune
Pune Call girls
Call girls in Pune
Pune Escort
Independent Pune Escorts Services

Pune Escorts Services
Pune Escorts
Escorts in Pune
Pune Call girls

Pune Escort
Independent Pune Escorts Services

Pune Escorts Services
Pune Escorts
Escorts in Pune
Pune Call girls
Call girls in Pune
Pune Escort
Independent Pune Escorts Services









Pune Escorts Services
Pune Escorts
Escorts in Pune
Pune Call girls
Call girls in Pune
Pune Escort
Independent Pune Escorts Services

tiktokhotmodels said...

hyderabad escorts $$$
female hyderabad escorts $$$
independent hyderabad escorts $$$
hyderabad escorts ###
hyderabad escorts ###
Call Girls In Hyderabad ###
hyderabad escorts ###
Escorts Service Hyderabad ###

Aurum Escorts said...

The Bangalore escorts service strictly follow the norms and other terms and conditions of any standard escort service.

👉 https://managewp.org/members/56308/aurum-escorts
👉 http://impression3d.laposte.fr/en/users/aurumescorts
👉 http://guildwork.com/users/aurumescorts
👉 http://www.folkd.com/user/aurumescorts16
👉 https://godotengine.org/qa/user/aurumescorts01
👉 http://ttlink.com/aurumescorts01
👉 http://findnerd.com/profile/publicprofile/aurumescorts/

Madhu Escorts said...

They will listen to you quietly and with patience if you want them so. Many people hire escorts just to talk because they have called.

👉 https://www.650sforum.com/forum/members/21015-madhuescorts01.html
👉 https://www.bloglovin.com/@madhuescorts
👉 https://www.buzzsprout.com/942217
👉 https://www.yaarikut.com/user/madhuescorts01
👉 https://managewp.org/members/56340/madhu-escorts
👉 http://impression3d.laposte.fr/en/users/madhuescorts01
👉 http://guildwork.com/users/madhuescorts01

trishikakapoor said...

mumbai escorts ###
college call girls in mumbai ###
juhu call girls ###
andheri call girls ###
malad call girls ###
kandivali call girls ###
borivali call girls ###

trishikakapoor said...

mumbai escorts ###
college call girls in mumbai ###
juhu call girls ###
andheri call girls ###
malad call girls ###
kandivali call girls ###
borivali call girls ###

Madhu Escorts said...

The Greater Kailash Escorts will help you achieve what you want. Talk all you want with them or indulge in your carnal pleasures, you can do anything with them.

👉 https://www.blogger.com/profile/07747390120673015075
👉 http://chutpatti.com/user/madhuescorts
👉 https://profile.hatena.ne.jp/madhuescorts1/
👉 https://moz.com/community/users/14317103
👉 http://rivr.sulekha.com/madhu-escorts_46538612
👉 https://www.patreon.com/user/creators?u=31462570
👉 https://www.kongregate.com/accounts/madhuescorts01
👉 https://independent.academia.edu/MadhuEscorts

Sweety Khan said...

You want to become a Escorts In Hauz Khas, then you have to know really well about the area where you are going to work and know about clients.

👉 https://www.blogger.com/profile/13928431937830789479
👉 http://chutpatti.com/user/sweetykhan01
👉 https://profile.hatena.ne.jp/sweetykhan01/profile
👉 https://moz.com/community/users/14317919
👉 http://rivr.sulekha.com/sweety-khan_46541814
👉 https://www.patreon.com/user/creators?u=31466418
👉 https://www.kongregate.com/accounts/sweetykhan01
👉 https://independent.academia.edu/SweetyKhan8

Ahana Khan said...

Independent Escorts in Delhi
http://www.makeyourmood.in
Escorts in Delhi
Delhi Escorts
Escorts Delhi
Russian Escorts in Delhi
Russian Escorts in Delhi
Russian Escorts in Delhi
Russian Escorts in Delhi
delhi escorts
escorts in delhi
delhi escorts russian
Delhi Escorts
Delhi Escorts Russian
Russian Escorts in Delhi
Delhi Escorts
Independent Delhi Escorts
Independent Escorts in Delhi
Escorts in Delhi
Delhi Escorts
Escorts in Delhi
Delhi Escorts
Mahipalpur Escorts
escort in mahipalpur
aerocity escorts
escort in aerocity

Aditi Reddy said...

Visakhapatnam Escorts
Visakhapatnam Escort
Visakhapatnam Escorts Agency
Vizag Escort
Visakhapatnam Escorts Service
Independent Visakhapatnam Escorts
Independent Visakhapatnam Escort
Visakhapatnam Female Escorts
Visakhapatnam Escorts Girl
Escorts in Visakhapatnam
Escorts Service in Visakhapatnam
Escorts Girl in Visakhapatnam
Visakhapatnam Erotic Girl
Visakhapatnam School Girl
Visakhapatnam House Wife
Vizag Call Girl

Kochi Escorts
Kochi Escort
Kochi Escorts Agency
Kochi Escorts Service
Independent Kochi Escorts
Independent Kochi Escort
Kochi Female Escorts
Kochi Escorts Girl
Escorts in Kochi
Escorts Service in Kochi
Escorts Girl in Kochi
Kochi Erotic Girl
Kochi School Girl
Kochi House Wife

Unknown said...

Pune Escorts

Pune Escorts Services

Pune Call girls
Call girls in Pune
Pune Escort
Independent Pune Escorts Services

Pune Escorts Services
Pune Escorts
Escorts in Pune
Pune Call girls
Call girls in Pune
Pune Escort
Independent Pune Escorts Services

Pune Escorts Services
Pune Escorts
Escorts in Pune
Pune Call girls

Pune Escort
Independent Pune Escorts Services

Pune Escorts Services
Pune Escorts
Escorts in Pune
Pune Call girls
Call girls in Pune
Pune Escort
Independent Pune Escorts Services









Pune Escorts Services
Pune Escorts
Escorts in Pune
Pune Call girls
Call girls in Pune
Pune Escort
Independent Pune Escorts Services

Ahana Khan said...

Independent Escorts in Delhi
http://www.makeyourmood.in
Escorts in Delhi
Delhi Escorts
Escorts Delhi
Russian Escorts in Delhi
Russian Escorts in Delhi
Russian Escorts in Delhi
Russian Escorts in Delhi
delhi escorts
escorts in delhi
delhi escorts russian
Delhi Escorts
Delhi Escorts Russian
Russian Escorts in Delhi
Delhi Escorts
Independent Delhi Escorts
Independent Escorts in Delhi
Escorts in Delhi
Delhi Escorts
Escorts in Delhi
Delhi Escorts
Mahipalpur Escorts
escort in mahipalpur
aerocity escorts
escort in aerocity

iGet Solutions said...

Every person want to become popular at their business category but it is not easy task to become famous. Lots of peoples spend huge amount of money to advertise their business or can say more visibility on online presense. If you want to become famous list your business in iGet Solutions to increase your sales. To Know more about us get in touch with us at

Online Business Directory
Business Directory
Online Business Portal
Business Portal
Business Listing Website
Business Listing Sites
Listing Website
Online Local Business Portal
Local Business Portal
Online Local Business Directories

spaking said...

Escorts in Gurgaon
Escorts in Haridwar
Escorts in Haridwar
Escorts in Haridwar
Escorts in Haridwar
Escorts in Jaipur
Escorts in Jaipur
Escorts in Jaipur
Escorts in Jaipur
Escorts in Kolkata

meera khan said...

Call Girls in Chandigarh
Chandigarh Call Girls
Escort Service Chandigarh
Chandigarh Call Girls
Chandigarh Escorts Service
Call Girls Chandigarh

Escort Service Chandigarh
Call Girls in Chandigarh
Chandigarh Escorts
Call Girls Chandigarh
Chandigarh Escort Service
Chandigarh Call Girls

Independent Bangalore Escorts Services said...

All friends are invited in my house. i have arranged a dj birthday celebration this day.but I want a good-looking boy dance partner with me. Who one supply me fun and completely enjoyment.fascinated then
contact fast.

Bangalore Escorts

Bangalore Escort

Bangalore Escorts Service

Bangalore Escorts Agency

Independent Bangalore Escorts

Independent Bangalore Escort

Escorts in Bangalore

Escorts Service in Bangalore

Unknown said...

Hyderabad Escorts

Hyderabad Escorts Services

Hyderabad Call girls
Call girls in Hyderabad
Hyderabad Escort
Independent Hyderabad Escorts Services

Hyderabad Escorts Services
Hyderabad Escorts
Escorts in Hyderabad
Hyderabad Call girls
Call girls in Hyderabad
Hyderabad Escort
Independent Hyderabad Escorts Services

Hyderabad Escorts Services
Hyderabad Escorts
Escorts in Hyderabad
Hyderabad Call girls

Hyderabad Escort
Independent Hyderabad Escorts Services

Hyderabad Escorts Services
Hyderabad Escorts
Escorts in Hyderabad
Hyderabad Call girls
Call girls in Hyderabad
Hyderabad Escort
Independent Hyderabad Escorts Services









Hyderabad Escorts Services
Hyderabad Escorts
Escorts in Hyderabad
Hyderabad Call girls
Call girls in Hyderabad
Hyderabad Escort
Independent Hyderabad Escorts Services

«Oldest ‹Older   1201 – 1230 of 1230   Newer› Newest»