Help Wanted - Global File Server Designing

SETTING UP A GLOBAL FILE SERVER WITH A HOT DR BACKUP

XYZ Ltd is a global fund management company with offices in Singapore, Sydney and Malaysia.

Each office has a local file server that would be shut down at the end of the working day
thus only accessible at each location’s office hours. As operations become more global,
there is a need for a global file server that is accessible 24 / 7.
The global file server has to be able to perform a 2-way synchronization to ensure the
latest copies of files are updated to the global file server and to each local file server at
any point in time wherever the file may be updated, either from the global file server or
local file server.
A hot backup has to be set up for the global file server so that if the production global file
server crashes, the backup can immediately be activated and retrieve the latest, most
updated files, with minimum downtime and virtually zero impact on operations. Users
have to be able to continually access their latest working files.

Task

Assuming each office in Malaysia, Singapore and Australia, has one file server each, the
Environment Specification and details for each file server are listed as follows.
Server A (Malaysia):
OS: FREEBSD 6.1
Applications: OpenLDAP, Samba
Bandwidth: Upstream 512Kbps, Downstream 1 Mbps

Server B (Singapore):
OS: CentOS 5.3
Applications: OpenLDAP, Samba
Bandwidth: Upstream 768Kbps, Downstream 2 Mbps

Server C (Australia):
OS: Windows 2003 Server
Applications: Active Directory, Network FileSharing
Bandwidth: Upstream 1Mbps, Downstream 4 Mbps

Requirements:

1. All servers are hosted locally in the office.
2. Server A and B will start its service from 8:30am to 7:00pm (Malaysian Time).
3. Server C will start its service from 9:00am to 6:00pm (Australian Time).
4. The Marketing Manager and Higher Management will need to access files in
these servers at any time and from any where in the world.
5. Files stored in the file servers vary in sizes from 1Kb to 200Mb.
6. All applications, protocols and communications tools must be on open source
framework or developed internally.
7. Communication channels between clients and servers must be tightly secured.
8. Any changes to the central server will be automatically copied and thus reflected
in the local server.
9. Changes to files must be logged, and can be audited by IT staff.
10. Average file sizes are around 10Mb, must be able to be opened within 1 to 2
minutes.
11. There must be a backup for every file, just in case users accidentally remove the file.

According to the specifications and requirements stated above, you are expected
to come up with a working prototype of a system (Global File Server) that can
meet the above requirements. Include all relevant network diagrams, UML
diagrams and flowcharts in your answer.
List all the applications, protocols and monitoring tools that are used in the
system in as much detail as possible.
Explain the strengths and weaknesses of the prototype system and how the
system can be improved.
The system must be accompanied by a Disaster Recovery plan.

I will give you some overview of your needs. On your post, you have mentioned the avg file size is 10MB and the file should be available in 1 - 2 minute which is 120secs (max) and the slowest avaiable upstream 512kbps.

First question, does the 512kbps your allocated bandwidth for file sync purpose or it is available bandwidth of your connection to ISP?

If the answer your allocated bandwidth, let us calculate and make some assumption. Just drop every protocol overhead and let say you could have stable 512k (64kBps) speed to the global server.

10 x 1024KB / (64KBps) = 160s

single file sync will cost you almost 3 minute. I don't know how many user working on the slowest side. If there are 3 user at the same time uploading 10MB file for sure the needed time will be 3 times longer.