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  1. #1
    Join Date
    Apr 2009
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    Understanding Cloud computing ( in a techinical way )

    Hello,

    I have been reading some articles about cloud computing and even saw some companies advertising on adwords ( some of them seems to be selling simple VPS ). But i still didn't got how i can build one.

    How does it work in a techinal way?

    If i have a openvz container that is moved to other host server when the current one fails, is this considered cloud computing? ( from the user perspective, the service is still up, right? )

    Are there specific softwares for cloud computing?

    Thanks,

    Fernando.

  2. #2
    Greetings Fernando:

    There are many ways to approach cloud computing.

    Examples today are Amazon.com, vps.net, slicehost.com among a number of others.

    One of the ways hosting providers are approaching cloud hosting is to have two to many physical servers (hosts) which have one to many guest operating systems (vps nodes) that can be migrated, replicated, etc. among the physical servers as needed.

    Parallels methodology might work for Cloud Hosting, but they would be my last choice for a variety of reasons. Right now, leaders in Cloud Hosting are VMWare and Citrix XenServer.

    Thank you.
    ---
    Peter M. Abraham
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  3. #3
    Join Date
    Apr 2009
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    Hello,

    Thanks for your answer!

    So, we can consider it as a HA VPS? As it will be available on two or more host servers.

    Does those softwares that you mentioned share resources between host servers?

    I mean, does one of the host servers keeps running the VPS and, when it fails, the other one start running them? Or is the VPS running on multiple servers in a cluster ( like kerrighed or other cluster solutions )?


    I am not really sure how it reduce costs ( this is one of the main thing that companies advertises ). Basically if now i need two or more servers to run a VPS, the costs should increase.

  4. #4
    Good day, Fernando:

    Yes, a high availability VPS can be considered a cloud.

    VMWare and Citrix XenServer allow you to easily move guest operating systems (vps nodes) between physical servers (requires a SAN) along with automatic moving of nodes on down physical servers if properly set up.

    Building a cloud can be quite and investment; and typically only pays if you can decrease the number of physical servers compared to what is currently in use.

    Thank you.
    ---
    Peter M. Abraham
    LinkedIn Profile

  5. #5
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    Quote Originally Posted by Fernando Marcelo View Post
    Are there specific softwares for cloud computing?
    Check out AppLogic - it's based on Xen, but it distributes the VMs across multiple physical servers with an automatic failover. If you have two AppLogic grids in different datacenters you can also do some really cool solutions with replication and complete failover to separate data centers.
    Jo Stonehouse, Kualo Ltd.
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  6. #6
    I'm just curious... for cloud computing, any servers (or virtual servers) within the grid can respond to requests. And this is possible due to replication. Does it also mean that data residing in a database is also replicated in a similar way?

  7. #7
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    Quote Originally Posted by cyberdigi View Post
    I'm just curious... for cloud computing, any servers (or virtual servers) within the grid can respond to requests. And this is possible due to replication. Does it also mean that data residing in a database is also replicated in a similar way?
    What type of cloud computing are you referring to? In something like Mosso or MediaTemple's system (which in cloud terminology is a 'Platform as a Service') database services would usually be clustered to improve headroom and to remove a single point of failure. Then you will have multiple clusters, and different customers assigned to difference clusters.

    Most Platform as a Service systems don't replicate data across web servers (which would be wasteful of resources), but rather, the web servers will use shared storage. If data was replicated, it would be closer to a CDN (which typically only serve static files).
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  8. #8
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    Quote Originally Posted by dynamicnet View Post
    One of the ways hosting providers are approaching cloud hosting is to have two to many physical servers (hosts) which have one to many guest operating systems (vps nodes) that can be migrated, replicated, etc. among the physical servers as needed.
    So far, the above definition works for VPS. It does not differentiate VPS from Cloud.

    Quote Originally Posted by dynamicnet View Post
    Yes, a high availability VPS can be considered a cloud.
    I would have to disagree. Cloud is not just a HA VPS. We have HA VM (based on Citrix XenServer Platinum), but we won't call it cloud.

    There are many definitions of cloud, but I will argue yours shouldn't be one.

    Again, I would disagree that HA VM/VPS is a cloud.
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  9. #9
    Quote Originally Posted by dazmanultra View Post
    What type of cloud computing are you referring to? In something like Mosso or MediaTemple's system (which in cloud terminology is a 'Platform as a Service') database services would usually be clustered to improve headroom and to remove a single point of failure. Then you will have multiple clusters, and different customers assigned to difference clusters.

    Most Platform as a Service systems don't replicate data across web servers (which would be wasteful of resources), but rather, the web servers will use shared storage. If data was replicated, it would be closer to a CDN (which typically only serve static files).
    Thank you for your explanation. Yes, I'm referring to platform as a service. It makes sense not to replicated the data but instead have s shared SAN storage that could also be clustered for redundancy. Thanks.

  10. #10
    Quote Originally Posted by FHDave View Post
    So far, the above definition works for VPS. It does not differentiate VPS from Cloud.



    I would have to disagree. Cloud is not just a HA VPS. We have HA VM (based on Citrix XenServer Platinum), but we won't call it cloud.

    There are many definitions of cloud, but I will argue yours shouldn't be one.

    Again, I would disagree that HA VM/VPS is a cloud.
    Would you consider a HA VM/VPS a cloud if the HA is a hot standby i.e. server active servicing requests via a load balancer? Cold standby servers for HA purposes certainly does not qualify as a cloud.

  11. #11
    It would seem there is a grey area here in the explanation. What it seems like is you're looking for a solution that would be load balanced with HA.

    In a cloud scenario you would have at least three server nodes that had a vps running on two of those nodes. You would then load balance the two vps's and setup HA on each. Should one of the vps's go down it would be automatically restarted on the third node. Having load balancing would then give you the up time you require as all requests would be sent to the vps that is up while the other vps was restarted.

    In a cloud such as this the vps are running on the nodes and the vps data is kept on some form of centralized storage. The nodes are only used for processing while the writing of the data is done to the centralized storage node. This way if a node goes down there is no data loss, provided the centralized storage is replicated or at least backed up regularly.

    In what I've described above there would be at least 5 server nodes. 3 processing and two storage. The storage servers would be replicated. You might possibly need more nodes depending on what cloud solution you're using since there would be a management node and possibly other services you need to run.
    Matt Kelly
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  12. #12
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    Notice how everyone describes "Cloud Computing" differently... It's not one thing, it's many different things to many different people but at the end of the day, no matter what it's called, we're still just dealing with computers attached to a network providing services to end users.

    Cloud computing to me is the idea to scale quickly (up and down) by utilizing shared resources (physical or virtual). For instance, VPS's managed by Xen with a mix of iSCSI & NFS storage, LDAP+Kerberos, load balancers and a master-master SQL cluster is what I present to my clients as a "cloud". They are not burdened with the complexities of how everything works, they are simply given an interface to manage their data and services. As their needs/traffic increase more Xen nodes can be provisioned and assigned different tasks to ensure their specific applications run in the most efficient and optimal way.

  13. #13
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    Quote Originally Posted by fatbox View Post
    Notice how everyone describes "Cloud Computing" differently... It's not one thing, it's many different things to many different people but at the end of the day, no matter what it's called, we're still just dealing with computers attached to a network providing services to end users.

    Cloud computing to me is the idea to scale quickly (up and down) by utilizing shared resources (physical or virtual). For instance, VPS's managed by Xen with a mix of iSCSI & NFS storage, LDAP+Kerberos, load balancers and a master-master SQL cluster is what I present to my clients as a "cloud". They are not burdened with the complexities of how everything works, they are simply given an interface to manage their data and services. As their needs/traffic increase more Xen nodes can be provisioned and assigned different tasks to ensure their specific applications run in the most efficient and optimal way.
    Agreed -- great synopsis.

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  14. #14
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    Quote Originally Posted by fatbox View Post
    Notice how everyone describes "Cloud Computing" differently... It's not one thing, it's many different things to many different people but at the end of the day, no matter what it's called, we're still just dealing with computers attached to a network providing services to end users.

    Cloud computing to me is the idea to scale quickly (up and down) by utilizing shared resources (physical or virtual). For instance, VPS's managed by Xen with a mix of iSCSI & NFS storage, LDAP+Kerberos, load balancers and a master-master SQL cluster is what I present to my clients as a "cloud". They are not burdened with the complexities of how everything works, they are simply given an interface to manage their data and services. As their needs/traffic increase more Xen nodes can be provisioned and assigned different tasks to ensure their specific applications run in the most efficient and optimal way.
    I completely agree.

  15. #15
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    Agree

    That is perfect.
    Choose the definition according to your requirements!
    Quote Originally Posted by fatbox View Post
    Notice how everyone describes "Cloud Computing" differently... It's not one thing, it's many different things to many different people but at the end of the day, no matter what it's called, we're still just dealing with computers attached to a network providing services to end users.

    Cloud computing to me is the idea to scale quickly (up and down) by utilizing shared resources (physical or virtual). For instance, VPS's managed by Xen with a mix of iSCSI & NFS storage, LDAP+Kerberos, load balancers and a master-master SQL cluster is what I present to my clients as a "cloud". They are not burdened with the complexities of how everything works, they are simply given an interface to manage their data and services. As their needs/traffic increase more Xen nodes can be provisioned and assigned different tasks to ensure their specific applications run in the most efficient and optimal way.

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