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VRTX - number of spans for Raid10
Hi,
Can someone please explain what exactly does "number of spans" mean when creating a RAID10 virtual disk in VRTX's CMC?
I have 8x 900GB drives, and when I choose to create RAID10 and select all the drives, I'm able to set the "number of spans" to 2 or 4. In both cases, the virtual disk can be max. ~ 3,1TB, so it definitely isn't creating any additional mirrors.
Would be grateful for an explanation, as I'm worried this setting could have an impact on the RAID's reliability.
DELL-Geoff P
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February 24th, 2014 10:00
Michalz,
I would set it to 4 spans. Here is the reasoning:
In a RAID 10, you can lose 1 drive per pair and still remain functional. If you use only 2 spans, you can only lose 1 drive per span and remain functional. With 4 spans, you can lose up to 4 drives in this scenario.
Hope this answers your question.
Regards,
MichalZ
2 Posts
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February 24th, 2014 10:00
Thanks Geoff,
So what you're saying is:
- 4 spans means striping across four RAID1 pairs (essentially RAID1+0)
- 2 spans means creating a mirror of a 4-disk stripe (RAID0+1)
Am I getting this right? Is there a sensible use case for the 2-span scenario (I can think of none)?
Best regards,
DELL-Geoff P
990 Posts
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February 24th, 2014 11:00
MichalZ,
I discussed this with one of our hardware specialists; he recommended we go with the 4 spans vs 2 spans for the reasons of redundancy. In the grand scheme of things, its still a RAID 10.
Regards,