raid 0+1

[???_185]

is it same raid configuration betweeen 0+1 and 1+0?

[Srinivasa_6]

Yep - they both mean the same (Striped Mirroring) and they might be used interchangeably.

[Uwe Zessin]

I don't recall if there is any standard that describes what is what (striped mirrors vs. mirrored stripes). I never use 0+1 or 1+0, but always talk about SM or MS to avoid confusion.

[Srinivasa_6]

I stand corrected. In fact, there is a slight difference.

http://www.ofb.net/~jheiss/raid10/

[DragomirAtea]

Hi folks!

In my humble opinion there is a huge difference...

Mirrored stripes is dangerous to use!
They are infact two stripes that you mirror.

If you loose 1 diskdrive, the entire stripe will be lost, and youre running on a RAID 0. That means that you can only loose one disk in that configuration.

Stiped mirrors on the other hand, is multiple mirrors that you stripe. That means that you can loose 50% of your drives and still be up and running.

I would never set up a mirrored stripe in a working enviroment.

But..
Who says that I'm allways right, actually I was wrong once in 1976. (-;

Regards
Dragomir Zekic

[John Kufrovich]

Dragomir, your explanation is almost correct.

If you loose a drive from each set you loose access to your LUN.
With 0+1,
Drives 1 2 3 4
Set 1 = 0 0 0 0
Set 2 = 0 0 0 0

Set 1 is striped and Mirrored with Set 2. If you loose a drive in Set 1, say dr2. No problem you have set 2 for backup. BUT if you loose ANY drive in the Set 2. Then you have lost all access.

With 1+0
Drives 1 2 3 4
Set 1 = 0 0 0 0
Set 2 = 0 0 0 0

Each drive from each set is Mirrored with each other, then striped. SET 1 DR1 is Mirrored with SET 2 DR1. Then continue down the line. If we loose DR2 of set 1, no problem, we have the other drive2 as a mirror. The only time you could loose access if you lost drive2 of the Set 2. As Dragomir stated, you can loose 50% of your drives as long as the drive isn't the mirrored pair.

It is a matter of odds.
BTW, MSA and Smart Array Controllers do Raid 1+0.

[Basil Vizgin]

John,
how can I find what drives are in pair in raid 1 part of RAID1+0 array on SA (MSA) controllers?
If I split 1+0 array between 2 channels, are the members of pair on different channels?

This is important to understand how can array in MSA survive with enclosure failure.

[Shameer.V.A]

Hi zungwon ,
Please find the attached document. Hope this will help you to clarify..

Regards,

Shameer

[John Kufrovich]

Basil,

Take 6 drives, 3 from shelf A and 3 from shelf B. Disk A1 and B1 will be mirrored. A2 and B2, ...

[Basil Vizgin]

Thank you, John!