August 18, 2014

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What Is Shared Storage and When Should I Use It?

netapp filer

Shared storage is a NAS (Network Attached Storage) device that acts as repository of shared file data.  In essence, it is a large, redundant, high performance file server.

Let’s discuss some different options for clustered file storage.

Let’s say you have an application where customers upload documents and those files need to be immediately available to multiple web servers.  There are three technical approaches you could take, each having various pros and cons.

1) Replicate a copy of the file to every server.  If a file is updated on one server, software can be used to replicated the required files to all of the other web servers.

  • Pros: – Fastest file access for local storage (usually best for code)
  • Cons: – Replication is computationally intensive
    – Requires replication software
    – Complex to manage with no file locking
    – Replication has a delay
    – Inefficient use of storage
    – You have as many copies of your data as you do servers. ie 1 Gb of data * 5 nodes in your cluster, means that 1gb uses 5 Gb of space.

2) Use a server as a file repository.  You could have a single server that acts as the file repository for all of your applications.

  • Pros: – Lowest cost per Gb for mid-tier scale 1Tb till about 3 Tb.
  • Cons: – Higher cost for low volume of high volume of storage
    – Single point of failure
    – Doesn’t scale to very large sizes
    – Difficult to backup

3) Use a NAS share – A NAS share is the best option for linear scaling of your storage from and to any size.  Instead of storing a copy of your file on every server, or having a single server as a potential point of failure, NAS devices have a tremendous amount of redundancy built into the platform; multiple brains, multiple paths, multiple shelves, all work in concert to ensure the availability of your data.

NAS allows for backups of very large volumes in a cost efficient manner.  NAS also support both CIFS (for Windows) and NFS (for Linux).

  • Pros: – Lowest cost per Gb for any scale
    – Accessible to Windows and Linux servers at the same time
    – High performance caching and automatic storage tiering
    – Grow on demand to any size
    – Almost no additional load on servers
    – Only data changes are replicated to offsite locations (very efficient)
  • Cons: – NAS is the right solution for shared database (that needs SAN)
    – Doesn’t perform well as a share code repository

NAS is a great fit if you have:

  • An application where users upload documents or images that need to be available immediately on all of your servers.
  • Your Content Management System (CMS) is configured where authoring and publishing are separated.
  • A large scale WordPress blog and/or CMS and need to share your wp_content or uploads folder
  • An Ecommerce platform which as an image repository

Edge relies on technology from NetApp, the best in the business when it comes to NAS.  Below is a typical hosting solution which utilizes NAS:

Edge netapp shared storage



NAS, can optionally be configured to autogrow.  Contact our support team if you would like to enable this feature on your volumes. Instead of running out of space, the NAS can simply become larger as you use it. Here are Edge’s parameters for autogrow:

Volume size  Trigger point 
< 20 GB 85%
20 – 100 GB 90%
100 – 500 GB 92%
500 GB – 1TB 95%
> 1TB 95%



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