Web/System server replication

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We are looking at new systems t run our entire business - one method that developers keep suggesting is running everything on the web, our multiple websites, internal systems, order processing the whole works.

We would only consider this if we could replicate the web hosted services with an internal server so that if our web connection goes down we could still continue to work and take orders with the systems syncronising once the connection was restored.

How would we go about this syncronisation and what equipment would be needed??
 
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I would concentrate on designing a fault tolerant system with the hosting provider over trying to fail over to your office. A good hosting provider should be able to provide an adequate amount of redundancy. This could be a good candidate for "cloud" stuff.
 
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The problem isnt with the hosting, we use a clustered hosting system.

The problem lies with the connection from the office to the 'net - we are rural and BT are crap but our only option for us so we need to be able to continue our work, taking orders from the post and telephone and processing them through the produciton systems which are potentially hosted remotely when the ADSL line fails.

We have to have remote hosting as customers need access to the sites to place orders - hence it must be in 2 places at once, either in complete sync or very close to it.
 
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You want a good HA system in place this can be achived with VMware/Multple servers/SAN

Personally Id have 1 ISP feed ideally 2 if you can afford it. Then 2 firewalls on active standby pairs. This then leading down to your servers running ESXi.

This would also mean you can reach your website from the back end.
 
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The problem isnt with the hosting, we use a clustered hosting system.

The problem lies with the connection from the office to the 'net - we are rural and BT are crap but our only option for us so we need to be able to continue our work, taking orders from the post and telephone and processing them through the produciton systems which are potentially hosted remotely when the ADSL line fails.

We have to have remote hosting as customers need access to the sites to place orders - hence it must be in 2 places at once, either in complete sync or very close to it.

Wosh, I missed the point. :p. Sorry.

I would imagine that any ISP will probably have to go via BT if you're rural. You could look at LLU providers maybe and reduce the reliance on BT. However, I can't imagine them having a decent SLA's.

Are you to far for SDSL? I had satellite at an office I worked at which was used in case of DSL failure. That could be an option. It was fairly slow but could be good enough for orders.

How many times has your DSL failed at the office?

I guess your developers could write an application that could store all orders then allow them to be imported into the hosted system? Either that or you could replicate databases. I've sync'd mysql DB's over SSL to a remote web server which worked fairly well. An import system may take a lot of complexity away, especially if you have weak DSL.
 
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Our exchange only has BT equipment, we are a mile from the exchange (in the old exchange building!) and can only have 8mb (haha) ADSL, nothing else.

Our exchange isnt LLU.

Our ADSL goes down several times a year, its been getting better but ANY outage with remote services would mean 0 business could happen without a local replicated server. The local version would also allow us to control the production process quicker and easier than pulling data over the 'net all the time.
 
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Ouch, where the hell are you, lands end? :p.

Not sure how much replication I'd want to do on a 8mb DSL line. :S.

Can you get 3g? I've seen some firewalls with 3g fail over which would allow you to connect to the external website.

I don't know your business but would a leased line be a non starter because of costs?

What operating systems do you use for the web stuff?
 
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Mid Dorset!!

Leased line out here is v.expensive so non-starter. We have our incoming firewall router with failover to either cable/2nd ADSL and/or 3G and have a 3G modem for emergency but in the sticks reception is poor too.

The OS on the hosting is primarily linux as its php based although we have access to windows/asp and a hybrid system at the click of a button if needed.

The actual replication should be pretty low, once the system is installed in either location a copy will be taken and the data placed in the other location using a flash drive/hdd - fform there daily/hoursly/live replication is merely customer data and order info which is probable no more than a few Kb an order and as we arent a multi-national we dont process thousands of orders a day. The biggest files to move are PDF's but again they are on the whole faily small and most would be created on the web server remotely so incoming mainly to our local replication for further processing which is a bonus as incoming is much better than outgoing on our connection.
 
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SQL data replication only really works one way.

If I was specing this, I would use SQL replication to keep the office up-to-date at all times, but implement a mechanism to record all relevant changes after a failure of the internet connection, and a mechanism to import them once the connection had been restored, at which point the slave would be reset and off you go again.

99% of this would be down to the developer though.
 
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I've done something similar to what you've done Mike but the reverse. All using Linux.

Basically Head Office had Linux DB / Web server holding order data in PDF and MySQL. I replicated MySQL to a slave server on tinternet and used rsync over SSL (with firewall rules and stuff) to replicate PDF's. It worked well.

If our VPS went down orders would be saved until it could reach the main DB over the WAN. Our key difference to your instance Slime101 is that we had a T1 line which proved very reliable and had a reasonable upload.

In essence you could use the above technologies to keep everything sync'd. I a full sync over flakey DSL is just going to be a complete nightmare.
 
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I cant imagine needing to do a full sync except when the system is comissioned for the first time.

With regards to the point Mikehiow made about both sources having changed and getting them back in sync - we intend on having 2 ranges of references for orders placed onto the system, this enables us to segregate internal and web sources and sync things up if the system goes down as they are unique and can never create the same ref from the seperate locations. Other info fed back and forth would be things like status updates which would be one direction only.
 
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Mid Dorset!!

Leased line out here is v.expensive so non-starter. We have our incoming firewall router with failover to either cable/2nd ADSL and/or 3G and have a 3G modem for emergency but in the sticks reception is poor too.

I'm sure I heard about a company running fibre in sewers in your neck of the woods - maybe worth you looking into it. It'll be a damn site more expensive than running DSL though. Maybe you could see about getting multiple SDSL lines and bond them together? I *think* if one fails then the whole connection doesn't fail so you could continue to work, albeit at a lower speed.

Not sure about the size of the company, but as you are running on a DSL connection, I can't imagine it has a huge number of employees. I would concentrate on building a fault tolerant system in house personally. To have a fault tolerant fibre internet connection is probably going to cost you a small fortune. So assuming you can't get SDSL and bond the lines the only way I can see is to keep things in house.

One last note on DSL - We have a business DSL line for testing. In addition we have a 100mbit circuit. The business DSL line recently went down for a whole month. Luckily it doesn't matter much to us... but it was proper rubbish service. ISP kept closing tickets, cancelling engineers etc. Unbelievable.
 
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H2O were running fibre in the sewers of Bournemouth - I've no idea if they ever took off or how far they got.

As for redundancy of connectivity, do you get 3G signal with any of the networks? It's pretty easy to set a dedicated machine that routes all of your internet traffic to fail over to a 3G connection. That said, if you are only really pushing SQL traffic in the event of your ADSL failing, then even GPRS may be an option - either way, this simplifies everything, as you have a centralised database, it is easy to run the application from multiple locations.

Given the relatively low cost of a second line and connection, you should really consider another line with another ISP which covers you in the event of an ISP failure. That way, you'd only be falling back to a 3G/GPRS connection in the event of a BT failure, which are usually less common than an ISP failure.
 
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Simple solution has to be satelite broadband alongside your BT connection so you then have two options for your conection. A cheap satelite conection would be slower than your BT broadband but plenty to keep you ticking over during the one or two outages a year you currently experience. Costs are also reasonable.
 
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larger enterprises that use SAN storage often use replication to another site but I think it would be very expensive for a SMB. I know StratoGen do an EqualLogic replication service http://www.stratogen.net/products/equallogic-replication.html

However, in your case I think it wuold be better to host your servers in a resilient data centre. Find a hosting provider that has multiple internet connections and the work is done for you. That way you just need a couple of ADSL lines in your premises from different providers and you have a great, resilient setup.
 
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