Real-Time RAID Dos and Don’ts

Do:

  • When using applications like torrent and the likes, do enable the option to preallocate the files. This helps create less fragmentation within the FlexRAID filesystem and increases performance and resource utilization. Also, when copying files, use a program that pre-allocate the file to be copied. Some programs fail to pre-allocate and end up creating too much fragmentation. Essentially, avoid using anything that creates too much disk fragmentation with RT RAID. If you must use such program, then you must create your RT RAID using a larger Minimum Allocation Size (See this forum post)

  • When copying files into the pool use Windows Explorer (or Linux equivalent). Avoid TeraCopy! TeraCopy fails to pre-allocate files and creates unnecessary fragmentation. Instead, and if you are not a fan of Windows Explorer, use tools like UltraCopier, FastCopy and KillCopy (make sure to configure them to pre-allocate on file copy if that’s not the default).

  • Increase your reserve space to 50GB or more. Once all your drives reach that mark, reduce it in 10GB decrements.

  • When starting with new drives with data on them, if a drive has less than 10GB free, do move some of its data to another drive such that each drive has at least 10GB free.

  • Test your system for stability. If your system is unstable, you will find yourself needing to reconcile the array on certain crashes (similar to disk scanning on Windows after a crash).

  • Always stop the storage pool through the WebUI before restarting the FlexRAID service or your OS. Windows systems will kill the service in as little as 5 seconds and usually in 15-20 seconds, which often does not leave FlexRAID with enough time to properly close up it resources.
    It is also recommended that you increase the WaitToKillServiceTimeout value to 300000. Read here: How to increase WaitToKillServiceTimeout
    This might increase the time it takes your system to reboot, but it will allow services enough time to properly shutdown.

Don’t:

  • Never write to the source drives. In fact, never attempt to browse the source drives as programs like Windows Explorer will silently write data to them. If you ever access the source drives, you should reconcile the array right after before starting the pool (or stop the pool and reconcile afterward).

  • When stopping the pool from the WebUI, do not get impatient and kill the service. Check the logs for what FlexRAID is doing and allow it to complete its operations. There might be time where stopping the pool will take a long time due to processing pending delete operations.

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2 Responses to “Real-Time RAID Dos and Don’ts”

  1. octoberasian July 15, 2012 at 11:10 PM #

    I’m curious:
    When Windows needs to restart after a Windows update or another program needs to restart, should I postpone the restart and stop the FlexRAID service everytime that happens?

  2. Jeff January 7, 2013 at 11:34 AM #

    TeraCopy actually preallocate files, using SetEndOfFile() and SetFileValidData() functions.

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