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Poweredge r710 Perc 6/i Only 1/4 of storage for raid 10
Long time lurker, first time poster looking for help with an R710 with an integrated Perc 6/i controller.
I have 8 drives with 600GB of storage each and am trying to set up a raid 10. When I go to configure it to create 2 spans with 4 drives each I should have at least 2TB of space per mirror, but I am only getting 1167GB. I have not updated or changed any settings and have not installed an OS on it yet.
If anyone can help me figure out why this is, that would be most appreciated.
DELL-Daniel My
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June 5th, 2018 09:00
Going beyond a span length of 2 is referred to as enhanced RAID 10. It is a way to create RAID 10 virtual disks larger than 16 drives. You are only using 8 drives, there is no reason you should increase the span length. All you need to do is leave the span length at the default of 2 and select all 8 drives instead of 4. If you want read more on how enhanced RAID 10 works then you can read this article.
www.dell.com/support/article/sln111362/
DELL-Daniel My
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June 4th, 2018 16:00
Hello
I don't think you are setting the options the way you think. When you choose the number of disks you are choosing the total number of disks, not the number of disks for one mirror. Also, the span that you are selecting is not the number of spans, it is the span length.
If you are choosing a span length of two and number of disks as 4, then it would be:
Two sets of RAID 1 mirrors, the two RAID 1s are connected by a RAID 0. This would give you roughly 1.2TB of space. The span length determines how many minimum disks are required, or how big the sets are that they can be added. You should not change span length unless you are creating a RAID 10 that has so many spans it exceeds the number of spans supported by the controller. The default span length is 2. RAID 10 is a minimum of 4 disks. With a span length of two you can have a RAID 10 of 4, 6, 8, 10, 12, etc total disks. Most of our RAID controllers have a span limit of 8, so if you wanted to create a RAID 10 of more than 16 drives you would need to increase the span length. If you set the span length to 4 then you can create a RAID 10 of 4, 8, 12, 16, 20, etc total drives until you hit the drive or span limit.
You should be able to leave the span length at 2 and use all 8 drives to accomplish the RAID 10 you are wanting. It should have ~2.4TB of usable space.
http://www.dell.com/storagecontrollermanuals/
Thanks
Mcoolwhip
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June 5th, 2018 08:00
I do understand that setting the span length determines the number of physical disks per span. I just don't get how the raid controller configures the drives if it were to have a span length of 4, resulting in two spans of 4 drives when using a total of 8 drives.
It is odd because I was already able to create a virtual disk with a span length of 4 with two spans from the 8 drives but I am not sure how the controller is configuring it and I cannot think of how many drives could fail and what specific drives they would have to be for the virtual disk to fail.
I do get that if I set the span length to 2 that it would create 4 raid 1 pairs and stripe across all of the pairs, but what does it do with a span length of 4? Does it consider 4 drives as one big drive, striping across all of them and then mirroring this on the other span of 4 drives, or does it create more of a raid 100, striping across two raid 10's?
I just want to make sure I am creating a stable and reliable configuration. We might be using the server as a hyper-V host, hosting exchange services and a domain controller, or hosting domain controller and an SQL server, or using it as a citrix host server depending on what it might be best suited for.
Mcoolwhip
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June 5th, 2018 10:00
I have been looking for this exact kind of documentation! Thank you so much, been looking for days. :Crying: