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I'm shopping for a new server and have been using software RAIDs.

But I wondered about doing recovery on a hardware RAID vs a software one. I know with a software RAID you have to enter a series of commands to get the replacement drive working back in the RAID so it can re-sync.

What has to be done in a hardware RAID after you replace the failed hard drive? Is it easier and less time consuming than for a software RAID?

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    Easier depends on what type of failure you have with either one. On hardware raid you replace the drive and the raid controller will rebuild automatically in most cases, sometimes you have to trigger the rebuild process yourself using the raid firmware/software
    – Moab
    Commented Mar 21, 2016 at 3:23
  • With a hardware RAID, how is the trigger to rebuild done? Using regular CentOS commands or are these commands that communicate with the firmware for the hardware RAID?
    – Edward_178118
    Commented Mar 21, 2016 at 4:45
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    Hardware raid is either controlled by software you install in the OS or via directly the raid controllers firmware which can be edited during bios post by using a certain keystroke to enter the firmware utility before windows begins to load.
    – Moab
    Commented Mar 21, 2016 at 18:32

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Software RAID is safer from a recovery point of view from because you can put the remaining disks into any system which will read them - you do not need to worry about the specifics of the RAID controller.

The commands to re-add software RAID are really not that hard at all.

Removing a disk: mdadm --fail /dev/mdX /dev/disk-to-fail --remove /dev/disk-to-fail

Adding a new one (after partitioning it) mdadm --add /dev/mdX /dev/disk-to-add

Hardware RAID can often be easier as it can just be a matter of unplugging one disk and plugging in a replacement - and normally it will just rebuild itself.... which is fine unless the controller or PC goes Kaput. Chances of this happening are not high, but are non-zero.

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    Further, otherwise then swapping faulty disks, maintaining software RAID through the OS is easier under Linux then hardware RAID - Hardware RAID comes with specific tools, which are a pain-in-the neck to get, and an even bigger pain in the neck to use. (I HATE PERC CONTROLLERS !!!) I do note you can do a lot of stuff in BIOS, but that doesn't really help you if you want to fix stuff without shutting down the server and being at the console.
    – davidgo
    Commented Mar 21, 2016 at 8:37

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