[CentOS] Re: A question about RAID and partitions

[Scott Silva]

Miguel Medalha spake the following on 5/22/2007 1:53 PM:
> Perhaps I am wrong but I feel that my question didn't receive an answer
> yet; the discussion digressed a bit.
> So, let me rephrase my question:
> 
> Which one is better, RAID devices created on top of partitions or
> partitions created on top of RAID devices?
> 
> By "better" I mean under the aspects of data security, performance and
> ability to recover from a disk crash.
> 
Raid devices created on partitions would most likely be software raid as I am
not sure if you should create partitions on a software raid device, although
linux would probably let you.. The technology is mature and sound, and the
processor load is not that great.
Partitions on top of raid devices would most likely be hardware raid. Some
devices are better than others, not just the hardware, but the driver support.

You can not answer your question that easily, though. The "type" of raid
device you create is what will tell you how recoverable it is. A stripe or
raid 0 is not resilient at all. The loss of one drive will destroy your data.
How much you can recover would depend on the size of the stripes and the size
of the data. A mirror or raid 1 is infinitely more recoverable, because a
complete copy of the data is on each drive.
Raid 5 or better has a somewhat less chance of survival, but is better than
raid 0 chance of surviving.
None of them would be reliable enough to use without some sort of backup.
Data security shouldn't depend on the type of or lack of raid. Data is secured
by limiting access.
The better performing raid types aren't always the best for survivability.

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