NAS - 2 Large Drives Raid 1 - vs - 4 Smaller Drives Raid 10

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phor

phor

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Sep 24, 2007
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Assume a NAS is built as a file share that is accessed by several users.
As such, both read and write activity will be fairly high and files transferred could be small or large.

Since single drive capacities are topping 12TB these days, it seems there is a choice to be made.
Let's assume I want ~8TB of usable space.

  • I could accomplish that by buying 2 8TB drives and putting them in a single Raid 1.
    I could also accomplish that by buying 4 4TB drives and putting them in Raid 10.
The cost is virtually identical either way.
Which structure would you choose and why?
 
Solution
JaredDM
Personally, I'd probably do the two 8Tb drives vs the four 4Tb drives. A NAS is unlikely to see much performance advantage at RAID 10 vs 1 unless you're running it on 10Gib network. On a typical 1Gib connection it will be limited by the speed of the network which is actually slower than a single drive. That way you have more empty bays for later expansion.

However, cost may be a consideration too. I run mostly 4Tb drives in my RAID arrays because that's been a more economical size to buy than the larger ones (power considerations aside). But, I'm dealing with needing 96Tb of space, so that's a bigger factor on that scale.
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JaredDM

JaredDM

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Jul 8, 2015
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Personally, I'd probably do the two 8Tb drives vs the four 4Tb drives. A NAS is unlikely to see much performance advantage at RAID 10 vs 1 unless you're running it on 10Gib network. On a typical 1Gib connection it will be limited by the speed of the network which is actually slower than a single drive. That way you have more empty bays for later expansion.

However, cost may be a consideration too. I run mostly 4Tb drives in my RAID arrays because that's been a more economical size to buy than the larger ones (power considerations aside). But, I'm dealing with needing 96Tb of space, so that's a bigger factor on that scale.
 
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phor

phor

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In this specific case, the cost of 2 8TB drives is almost identical to 4 4TB drives. So cost isn't really a factor for me.

I didn't talk about the Networking, but I will have 4 1Gb-e ports available.
You are correct that a single person using the NAS will be bottlenecked by the network either way, but let's assume 2 or 3 are all accessing it at the same time. Single drive read/writes for these drives are somewhere around 150-180MB/s. That means if 2 people are using it, the network may no longer be the bottleneck.

So I think there are a few things to think about:
With the Raid1 there should be a lower risk of failure because there are only 2 drives, and either drive can fail. Single drive performance is slightly higher because larger drives come with more cache and have more platters. It also leaves room in the NAS for expansion.
With the Raid10, performance should be slightly better in a multiple user scenario, and if a HDD does fail, rebuilding the raid should take a lot less time.

Am I missing any advantages/disadvantages?
 
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failboat

failboat

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A Single disk nearly caps a 1Gbs network. The raid 10 won't increase your seq speeds much, unless you bond, which also requires a switch with the same feature.

The stripe on the raid 10 adds extra data loss risk due to not being able to rebuild the array.
 
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