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RAID Questions


jam3ohio
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Guys--

 

As we try to determine what's next in Vail, I am starting to look at RAID options, a totally new area for me. I have some questions that I'd appreciate feedback on:

 

  1. What types of RAID are possible on Server 2008 R2 using only the software RAID capabilities built into the OS?
  2. With data security as a priority, I understand that RAID 5 uses about 20% of storage to store parity info. At what hard drive count, and at what sizes, would the risk of failure really require RAID 6 and losing another 20% of storage for the increased parity data stored?
  3. How pricey are good RAID 5 and 6 compatible controller cards?
  4. If I implement a four disc RAID 5 today using a dedicated controller card, and I want to increase the amount of storage available in the future, what features do I need to look for on a controller card to allow for another array to be added to the system?
  5. What minimum level of hardware (processor, memory, PSU, etc.) needs to be onboard a system that could manage two 12TB arrays in RAID 5 or 6 configurations?
  6. Are enterprise class hard drives required in a RAID 5 or 6, or can we use green drives?

 

Just trying to get my arms around what I'd need to spend to get similar performance to WHS v1 on a Vail replacement (which may be Server 2009 R2). Any feedback is appreciated.

 

Thanks,

 

Jim

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And show 26 this Sunday ;)

 

Jam if you'll be on the live show tomorrow I would like us to answer these during the show.

 

OK will try at 11pm Pacific, no?

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For #2, the formula is simple. For RAID5, you have available (n-1)*the smallest drive size where n is the total number of drives. If you have 4 1TB drives, this is (4-1)*1Tb = 3TB. If you have 8 2TB drives, that is (8-1)*2 = 14TB. RAID6 is (n-2)*smallest drive, so in those cases it would be (4-2)*1 = 2TB and (8-2)*2 = 12TB.

 

EDIT: Spelling.

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My two cents...

 

What types of RAID are possible on Server 2008 R2 using only the software RAID capabilities built into the OS?

 

Basically, mirroring (RAID 1) and striping (RAID 0).

 

With data security as a priority, I understand that RAID 5 uses about 20% of storage to store parity info. At what hard drive count, and at what sizes, would the risk of failure really require RAID 6 and losing another 20% of storage for the increased parity data stored?

 

You math is a bit off. For RAID 5, take the smallest drive in your array, and then multiply it by the total number of drives minus 1. RAID 6 is similar, except you subtract 2. As far as when it makes sense to use RAID 6 over RAID 5, that's a tough nut to crack. Overall, however, I don't like to use more than 5 or 6 drives in a single RAID 5 array. No definitive logic behind it, that number just feels right to me somehow.

 

How pricey are good RAID 5 and 6 compatible controller cards?

 

For a home server? You can pick up an entry-level RAID controller no problem. You can find 8 channel units on NewEgg for between $200 and $300. You likely won't need onboard memory or battery-backed cache. I'd stick to business grade contollers, though, from Intel, LSI, 3Ware and Adaptec. You want something that a business would use to build a file server and still be able to sleep at night.

 

If I implement a four disc RAID 5 today using a dedicated controller card, and I want to increase the amount of storage available in the future, what features do I need to look for on a controller card to allow for another array to be added to the system?

 

Online expansion. Not all controllers support it, and others may support it poorly. The real challenge is the partition management in Windows. Expanding the size of your array may be fairly easy using the controller software, but you typically have to rely on 3rd party tools to expand the size of your partition. Otherwise, you'll have to take advantage of the extra space by creating a secondary partition and adding another drive letter to your Home Server.

 

What minimum level of hardware (processor, memory, PSU, etc.) needs to be onboard a system that could manage two 12TB arrays in RAID 5 or 6 configurations?

 

For 24TB of storage, I would consider either at least a Core 2 Quad or an i3 for my server and an extra slice of patience.

 

Are enterprise class hard drives required in a RAID 5 or 6, or can we use green drives?

 

Someone mentioned Western Digital RE drives in another post. These are basically desktop-grade drives that have passed a higher standard during testing. They are then flashed with different firmware to make them more controller friendly.

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OK will try at 11pm Pacific, no?

 

 

11am Pacific for the live show. We also had several discussions on show 25 and 25 with more to come. The upside is exciting performance.

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