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P410 controller and RAID 1 vs. RAID 1+0


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RAID 0/1

RAID 0/1 is also known as RAID 0+1, and it is sometimes called RAID 10. This combination of RAIDs provides the best of both worlds. It has the performance of RAID 0 and the redundancy of RAID 1. RAID 0/1 requires at least four disk drives to implement. In RAID 0/1, there are two RAID 0 stripe sets, which are used to provide high input/output performance, that are mirrored. This provides the fault tolerance. Figure shows a diagram of RAID 0/1.[/size][/font][/color]

It is 1+0 that is RAID 10 not 0+1, there is a difference right? Edited by g725s
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Not that I know of. And besides, how on earth would it work to mirror then stripe?


Basically, if data is being striped across drives, then the contents of files are spread out over more than one drive, which means no file is located complete on a single drive. If a single drive is pulled from the array, how can files be read from it? Of course, in theory, very small files, those smaller than the cluster size used on the drives, could be located on a single drive, but that's a special case and not likely to be of much use. Anyway, the allocation table is laid out as if there is more than 1 drive, so it wouldn't really be readable in standalone mode.

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Thanks very much for the article. I've never seen one quite like it. I wouldn't have thought it possible to stripe sets of mirrors, but I can see where it could happen. In fact, I suspect this is likely what most manufacturers actually implement, but of course I can't be sure.


In any case, I think the answer to your original question is still the same: i.e. you can't remove a drive from RAID10 or RAID01 and read it standalone. Whether a stripe of mirrors or a mirror of stripes, it's still striped, meaning data is spread out over multiple disks.

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The easiest way to remember the difference is to think about splitting the number up.


So think of Raid 10 as being Raid 1+0 (probably the better way of writing it but the manufacturers tend to drop the +sign). Start with the first digit (1) so we have a Raid 1 (mirrored) pair of disks. Take a number of these and then stripe them (the 0 part of the number) to form a single volume. So ten disks in Raid 10 would be five pairs of mirrored disks and all of these pairs are stripped together. You need a minimum of four disks and you need an even number of them.


Raid 0+1 works the other way round. Take a number of disks and make two separate stripped sets of them - then mirror the two sets.


Of the two, performance is broadly the same, capacity is identical but Raid 10 theoretically is more tolerant of disk failures than 0+1.


Similarly you can have Raid 50 and Raid 60 disk sets which are stripped sets of Raid 5 or 6 arrays.


And ikon is right, whenever you have a stripped arrangement even if it is as part of a composite raid setup then it is not possible to take any of the disks, put them in a different machine and have readable information on them.



Edited by jem101
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