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Recommended array/logical drive configuration

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Chris Wong_1
Advisor

Recommended array/logical drive configuration

So, we have an MSA1500 with four MSA30's connected to it. We've been configuring arrays and logical drives on each MSA30 using the same numbers of physical disks. For example: array 1 on 8 drives and logical drive 1 on array 1, and array 2 on 6 drives and logical drive 2 on array 2. But we've noticed that we could also configure all 14 disks in a single array and put multiple logical drives on that single array. Is that the way we should be configuring arrays and logical drives? It seems to use drive space more efficiently than how we are currently configuring our storage. Are there any negatives to using just 1 array across the entire MSA30...? For example, does a drive failure affect the entire array, or can we still lose 1 physical disk per logical drive if we configure two RAID 5 drives in the single array...?
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Patrick Terlisten
Honored Contributor
Solution

Re: Recommended array/logical drive configuration

Hello Chris,

yes, there are some limitations if you create only one array. You shouldn't mix disks with different capacities in one array. If you have applications, which cause a lot if I/Os, you should separate them on different arrays. There is a customer advisory from HP which you might find interesting:

Advisory: Degraded Read Performance with Multiple Logical Drives (LUNs) Configured to One Array Group with Specific Conditions

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&taskId=110&prodSeriesId=415598&prodTypeId=12169&objectID=c00622089

I always create more arrays, for example one array with LUNs for my blade server to boot from san. Or an array with LUNs for my exchange, or an array with LUNs for my fileservers. Every array has different LUNs and the array is split over two or three MSA30 enclosures to distribute the load.

Hope that helps.

Kind regards,
Patrick
Best regards,
Patrick
Chris Wong_1
Advisor

Re: Recommended array/logical drive configuration

Sure, that helps a lot. I have yet to find any docs that say to absolutely do or do not use a single array, but that article and your comments help clarify, in my mind, when and when I would not choose to do something like that. For a server that is going to use all 14 drives in a OS-level RAID 0 or spanned partition across the LUNs, it probably doesn't matter if I use 1 array or multiple arrays. But for a case where I will have multiple servers using each LUN for distinctly separate purposes, like a file server and VMware server, then I should use separate arrays as reads/writes affect the entire array. It sounds like there are no hard and fast rules, but the config should be based on desired performance and app-specific needs, etc...
Patrick Terlisten
Honored Contributor

Re: Recommended array/logical drive configuration

Hello,

correct. :)

What about some points. ;))

Kind regards,
Patrick
Best regards,
Patrick
Chris Wong_1
Advisor

Re: Recommended array/logical drive configuration

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