Maintaining a Transparent RAID array

Pre-requisite

Publishing (starting) a Transparent RAID array

The Tasks

The RAID maintenance tasks are really one function with 3 variations.
It is all about verifying the parity data against the user’s data to ensure that no bit rot is present.

The 3 tasks are:

  • The Verify task: this task verifies the array and stops at the first error encountered. It does not fix the error reported.
  • The Verify+ task: this task verifies the array and does not stop at the first error encountered. Instead, it does a complete verification of the whole array and then reports all errors encountered. It does not fix the errors reported.
  • The Verify/Sync task: this task verifies the array and overwrites the parity data where there is mismatch with the user data. It does this for the whole array and reports all errors it had to fix and the end.

Additionally, one can choose to run any of the maintenance tasks on a specific range of data rather than on the whole array.
You do that through the “Advanced Operations” menu.

1. Verify Operations

A range operation example: specifying a range for the Verify+ task. Here you can specify the start and end range to process.
Note: The range specified is relative to the size of the PPU (parity disks).
That is, specifying a range of 10GB and the array has 10 disks, then 100GB worth of data will be processed (10GB * 10 disks).
2. Range Operation

All RAID maintenance tasks can be executed on a Transparent RAID array while the array is either online or offline.
In fact, most tasks in Transparent RAID can be executed while the array is online or offline.

When a task is executing on an array, the task must complete before the array can be switched to being either online or offline.

Scheduling the maintenance tasks

TODO: link to scheduler topic
Using the Verify/Sync task as a RAID scrubber.


What’s next?

Performance tuning in Transparent RAID

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One Response to “Maintaining a Transparent RAID array”

  1. Dominic November 12, 2014 at 7:05 PM #

    Can you please provide a recommended “best practice” in terms of how often or in what situations we should run these Verify and Sync operations?

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