Monday, February 27, 2012

Storage Replication Overview - Part 2

steeleye block level replication

Introduction
In the previous article which I have cover in storage replication part 1. It cover the installation of the software and also the requirement. The software we are looking at will be SteelEye.

What is SteelEye?
As you know in some of the bigger organization, they will have big storage such as NetApps or IBM N series which could provide the storage replication capabilities. However if you do not have such high-end storage device. How can you achieve and have a business continuity as usual during disaster. This is a solution to replace a shared storage.You will know what I mean when you continue the journey together with me on SteelEye



This is a host base replication software which mean that it need to be installed on the host that you would like to replicate and also the target that is going to receive the replica copy of the files. They are a lot of consideration when you would like to use storage online replication such as bandwidth concern and etc.

With the software capabilities that built into it, it can solve your problem. This software built-in optimization feature which I am going to share later.

How does the replication work?
What does the software do is to mirror a volume one the source system and replicate the content of it to another server. This is a block level replication which occur at the disk layer or even the array layer. In the most common technology of storage replication it does provide 2 mode. It is very important for you to know the pros and cons regard to the 2 mode feature which is synchronous replication and also asynchronous replication.

Synchronous Replication
  • guarantees "zero data loss"
  • performance decreases as the application need to wait for the write transaction to be complete
  • it need to wait for the destination server in any write operation
Asynchronous Replication
  • write is considered complete as soon as local storage acknowledges it.
  • increase in performance.
  • remote storage is not guaranteed to have the latest version of the data.
Volume Consideration for mirroring
When you are going to plan for a drive for mirroring to a remote storage, you must take note on the following requirement that Steeleye that will filter out:
  • Windows system partition
  • Volume that contain page files
  • Non NTFS partition
  • Target volume are smaller than the source volume.

How it impact Hyper-V?
As mention, the software it is a volume base replication. This mean that if you store all the VHD into a single volume, all the VHD will replicated over to a remote storage once you configure it to sync. You might want to consider to relocate the lesser priority VMs into other volume.

Reference
Part 1 : Installing SteelEye Storage Replication software
Part 2 : Consideration Of Storage Replication 
Part 3 : Scenario of Storage Replication
Part 4 : Configure Storage Replication mirror
Part 5 : Configure cluster
Part 6 : Configure high availability VM(Live migration without shared storage)
Summary 
Stay tune with my next articles which I will going to deep dive into the certain scenario that we can use the software. Let us know what you though , learns and hope for next articles!. Connect with us on GOOGLE+ , TWITTER and FACEBOOK.

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