The Art of Storage: All things Storage

Jun 15 2010   7:10PM GMT

The Basics of File Virtualization

Graeme Elliott Graeme Elliott Profile: Graeme Elliott

In the file virtualization world, Network Attached Storage (NAS), NFS and file servers are referred to as back-end filers. I will use this term in the rest of this blog.

Once described to me as “DNS for files,” file virtualization offers a layer between your users and your business files, allowing for transparent policy-based migration and information life-cycle management. From a user’s perspective, the files that appear in a directory may actually exist on different shares on the same back-end filer or on different back-end filers. Using policies files can be migrated between different shares and back-end filers with total transparency to the users.

A file virtualization appliance (or cluster) is placed between the business users in your company and the file shares on your company’s back-end filers. This provides what is known as a Global Namespace as it consolidates and aggregates a number of or even all the file shares from the back-end filers into a single device (or cluster), providing a single access point to all files.

File virtualization appliances are offered by F5 (ARX Range),  EMC ( Rainfinity ), Auto Virt and Blue Arc’s File System products. Know of any additional file virtualization appliances? Please leave a comment.

These appliances can be used for ( to name a few ):

1. Migrating data between back-end files to aid in lifecycle management

2. Tiering by file type to lower storage cost (e.g. to migrate video and audio files).

3. Tiering by file age to lower storage cost (e.g. migrating files that have not been accessed for a given period of time).

The tiering of files can improve backup performance by migrating those files not required for backup (video, audio, or old files) to another tier. The backup software has fewer files to scan and fewer files for backup.

Some of these appliances offer migration to Hierarchical Storage Management (HSM) systems and Content Addressable Storage (CAS, an archiving platform) for further tiered processing such as putting the data on tape. I will go more in-depth about CAS in an upcoming blog post.

My own opinion on these appliances is that they are very expensive for what they do, so you will need a good business case to justify their use or have a specific use in mind. They do excel in life-cycle management, that is, migrating files to a new back-end filer when an old one is being replaced. With appropriate planning, only a small outage is required for the file virtualization appliance to start impersonating the old back-end filer and for seamless file migration to begin.

If you do have a specific use for these devices, I would love to hear about it so please leave a comment.

2  Comments on this Post

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  • Graeme Elliott
    Thanks Tsahy for your comments they are much appreciated. I have added AutoVirt to the article You are right that a lot of organizations are placing all their NAS technology behind these devices. One thing I didn't mention in the article is that failovers in the cluster are not as seamless as the vendors like to make out.
    80 pointsBadges:
  • Barabararohland
    What are the other options apart from NAS for File Virtualization?
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