Why is Real-Time RAID in Expert mode not supported?

Real-Time RAID in FlexRAID is implemented by trapping I/O requests on the virtual drive and channeling those requests to files spread across the source drives.

Reads and writes outside of the virtual drive cannot be trapped, and are outside of the control of FlexRAID.
For that reason, writing outside of the storage pool to the source drives is not supported in Real-Time RAID.

This is similar to bypassing your hardware RAID array and writing straight to the drives making up the array.
Doing such a thing is simply corrupting the array.

If you write outside of the pool when in RT RAID, you are essentially corrupting your FlexRAID storage pool volume.
That said, there is a way to recover from such corruption, which is to run the reconcile operation.
It is only because there is a way to recover that RT RAID is available as an option (albeit unsupported option) in the UI for those that like to thinker or very special cases.

Even if you think you will be careful and never intentionally write to the source drives, other programs and especially Windows Explorer tend to write to your data as you simply browse it. Windows will often update thumbnail information or user folder view preference information as you browse. Likewise, many media tools will update the media tags such as rating, number of time viewed, etc. as you play those media. So, what might seem like a read only operation is actually a set of read and write operations.

In Cruise Control mode, FlexRAID locks the drives such that only it has access to them. Once locked, the only way to access the data is through the storage pool, which is safe.
Essentially, the only reliable way to run RT RAID is in Cruise Control.

The average user looking for simplicity and reliability should never run RT RAID in Expert mode and should only run it in Cruise Control mode.

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One Response to “Why is Real-Time RAID in Expert mode not supported?”

  1. trent March 23, 2013 at 3:55 PM #

    So realtime raid write speed will be slower than snapshot mode. When i dident have my drives in a pool i was getting 79 mb sec write. Now i get 30mb.

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