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Unusual request…

Last week I was visiting a customer in Sweden for product training. One of the main reasons they required an on-site training was for a very unusual request:

The goal was a system with two RAID arrays configured as NAS volumes. Once one of volumes is full of data, it must be removed from the system then replaced with the new fresh and empty array. The full one must be shipped to another location where it has to be attached to another system and used for data analysis.

All the arrays swap need to be done online without a system reboot. This is really interesting to say the least as my thinking is: what kind of features require this from what applications? Luckily and thanks to an option where placing the RAID array to an offline position is possible. In this particular case the system was equipped with an ARECA RAID controller. Using the controller function of placing the RAID volume into offline state enabled me to remove all trays belonging to this array. Additionally after putting the arrays into offline mode all LEDs of the off-lined trays were blinking, so it was not a problem to identify the off-lined trays. In DSS V6 the volume group just disappeared of course with an error about missing volume group in the event viewer, but all the rest was working uninterrupted.

After inserting the array into the other system we just needed to click the re-scan function and all was properly recognized.

If you face a similar request please make sure you test it at least a few times before starting production. Also the best practice would require some data replication into the other system. The replication can be overwritten after successful shipping of the array to another location. Also the volume group name must be unique in the system, so every time you create new volume group please think about good unique name.

So, I hope that this unusual request is of some interest to you. Maybe you get customer request for archiving the data on regular bases. Such functionality can help you to think about hard disk based archiving solution.

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2 Comments

  • Matthias

    August 13, 08 2012 03:56:50

    Hi Janusz,

    I’m pretty sure this also works with 3ware controllers. This is the tiny difference between the options “remove unit” and “delete unit”. After selection “remove” you can pull one drive after another without turning the array into a degraded state.

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  • Janusz Bak

    August 14, 08 2012 02:32:27

    Yes, you are right. It will work with 3ware as well. It must work with every RAID which has a function similar to “remove unit” from 3ware.

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