raid 0+1

[dipesh_2]

Hi

There is a slight difference.

RAID 0+1 configuration where multiple disks are striped together into sets (sets A & B in the diagram, each set being as large as the resulting final volume), and then two or more sets are mirrored together.

RAID 1+0 configuration where two or more drives are mirrored together (mirrors 1-4 in the diagram), and then the mirrors (as many as are needed to result in the desired amount of space) are striped together.

[Sivakumar TS]

Hi Zung,

DEFENETLY IT IS NOT SAME

Simply

raid 0+1 ==> striping the mirrored volume

raid 1+0 ==> mirroring the striped volume

the redundancy differs in both config.
the mirror can survive a single disk failure and stripe cant.


With Regards,

Siva

[Uwe Zessin]

dipesh and Siva have exactly opposite definitions.

That's why I said I always talk about striped/mirrors or mirrored/stripes ;-)

[Basil Vizgin]

From MSA CLI Guide:

Note: If more than one pair of drives are included in a RAID 1 array, the data is
striped across the first half of the drives in the array and then each drive is mirrored to a
drive in the remaining half of the drives for fault tolerance. This method is referred to as
RAID 1+0.

[Adrian Parker]

Hi,

Using the CLI to create a 1+0 lun, will the MSA 1000 automatically mirror across enclosures if it can, or is the lun set-up based on the order of disks on the command line ?

Thanks,
Adrian

[Uwe Zessin]

It's my understanding that the MSA controller firmware is "smart" enough to use different enclosures on its own. I believe somebody from the MSA team said so some time ago here on ITRC, but I am not sure I could find the thread easily.

[Alzhy]

ZungWon,

Peace!

1. 0+1 and 1+0 both gives you the same capacity

2. AS far as redundancy - 0+1 (stripe and mirror) will be able to handle more disk failures.

3. Performance - it depends on where the RAIDing is done. If RAIDing is done on the host level say - using VxVM, and you are dealing with JBOD enclosures - one RAID scheme may be better than the other performance wise.

[John Kufrovich]

Nelson,

Please recheck your second statement.

RAID 1+0 offers more redundancy than 0+1.

RAID 0+1 will only handle a single disk failure in each mirrored set.

[Alzhy]

John you are absolutely right. RAID10 indeed is more redundant.

Take 8 disks, carve 4 mirror sets (RAID1), stripe(RAID0) accross this 4 mirror sets and you've RAID10. You can loose 1 disk from each mirror set and your stripe stays intact.

In VxVM, you have what's called layered Volumes. You can have a stripe of stripes, s stripe or mirrors, a stripe of RAID5's, etc.. further incresing the reliability and scalability of storage.

[Basil Vizgin]

Both 1+0 and 0+1 can handle same quantity of disk failures (for instance, second disk can fail in already failed half of 0+1 mirrorset). But probability of array failure with subsequentd HDD errors is much different (1/2 in RAID0+1 vs. 1/number of mirrors in RAID1+0).