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Dell H700 RAID 10 question

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David-Duc

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Hello guys, I have a question about RAID 10 array of 8 x SAS HDDs on Dell H700 controller:

1. If I configure the RAID 10 array to have 2 HDDs per span for a total of 4 span, the array (virtual disk) becomes RAID 0 stripped across 4 x RAID 1 (2 HDDs each). This mean the array can tolerate up to 1 HDD failure per span for a total of 4 HDDs failures and the array would still be functional, correct?

2. If I configure the RAID 10 array to have 4 HDDs per span for a total of 2 span, the array (virtual disk) becomes RAID 0 stripped across 2 x RAID 1 (4 HDDs each). This mean the array can tolerate up to 3 HDDs failure per span for a total of 6 HDDs failures and the array would still be functional, correct?

3. In both case, the total available storage would also be the same (half of 8 HDDs), correct?

Thanks in advance :D, and happy new year.

/I answered my own question: Dell controller does not support raid 1 for more than 2 drive in raid 10. When selecting 4 or more drives per span, it basically become raid 100 (raid 0 of raid 0 of raid 1).
http://www.dell.com/support/article/us/en/4/SLN111362/en
 
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RAID 10

Basically a RAID0 of two RAID1 arrays.

Depending on how you have your RAID0 spanned will determine how many drives you can lose.

Technically, the number of RAID1 components in the RAID0 will determine it.

2 RAID1s, you can lose 2 drives (one per array).
3 RAID1s, you can lose 3 drives (one per array).
4 RAID1s, you can lose 4 drives (one per array).

However, if you you lose BOTH drives in ANY of your RAID 1 arrays, you're screwed, blued and tattooed.
 
Chas said:
RAID 10

Basically a RAID0 of two RAID1 arrays.

Depending on how you have your RAID0 spanned will determine how many drives you can lose.

Technically, the number of RAID1 components in the RAID0 will determine it.

2 RAID1s, you can lose 2 drives (one per array).
3 RAID1s, you can lose 3 drives (one per array).
4 RAID1s, you can lose 4 drives (one per array).

However, if you you lose BOTH drives in ANY of your RAID 1 arrays, you're screwed, blued and tattooed.
Click to expand...
What I want to know is, if I set up a raid 10 with 2 spans consist of 4 HDDs each (8 HDDs total), would that result in 2 x RAID 1 (4 HDDs per RAID 1) that can tolerate up to 3 drives failure each span?

Basically it is a raid 0 of 2 x raid 1 with 4 drives each. Is that what the dell h700 does when you select 4 physical drives per span on raid 10 with 8 drives?

I know the most common raid 10 is to have 2 drives per span (raid 1). What I want to ask is, how the dell h700 behave when you select 4 physical drives each span with raid 10 8 drives instead of 2 physical drives each span.
 
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So, you have 8 drives total.

Four in Raid1a
Four in RAID1b

You then span them together using RAID0.

Yes, you could conceivably lose 3 drives from EACH RAID1 stack and still have an operational drive system.

What you MAY want to consider, instead, is two stacks of 3, with the 4th as a hot spare on auto-rebuild.
This way, if you lose a drive, the array begins reassembling itself immediately, and once done, you swap in a new hot spare.

It's recockulously wasteful of drive space. But if you absolutely, positively GOTTA have maximum uptime? It'll do the job.

And I recommend the RAID0 be HARDWARE RAID. Less chances of random software "burps" desyncing the stacks (which can lose you ALL your data).
 
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