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Two 512GB SSDs in RAID 1 vs four 256GB SSDs in RAID 10

6 posts in this topic

I was going to set up a VMware server with two 512GB SSDs in RAID 1. However, since 512GB SSDs are typically more than the cost of two 256GB SSDs, it occurs to me that I could do four 256GB SSDs in RAID 10 (aka RAID 1+0) and spend less.

If I understand RAID 10 correctly, in this scenario I'd have the same usable disk space, better redundancy (ie, I could survive 2 drive failures in my RAID 10 scenario as long as they're not in same RAID 1 set) and better performance. The only downside that I can think of is double the power consumption, but with SSDs that's not much of an issue.

Am I misunderstanding / missing anything here? Are there any other downsides?

Thanks in advance!

(In case it matters, I'm looking to do this with an LSI 9260-8i controller and Plextor M5 Pro drives once they hit the U.S.)

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No, your understanding is the same as mine. I would go with the smaller drives any time of the day since as you rightly put, you will get a much bigger benefit from the speed aspect of things. Just make sure that when you RAID 0 SSD's then TRIM etc does not always work so you may need to cleanwipe the drives every now and again. Apart from that, I would personally have opted for 8x128GB drives instead of 4x256GB since then you can even get more speed, plus chances are the RAID controller you've opted for will be able to handle 8 drives as well.

My 2 cents on the matter.

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I think going for four drives would be the best overall move, although I would be hesitant to move to 8 128GB drives instead. While you might see even greater performance, the cost of the system will rise, with the additional drive bay requirements, cooling around the mass of drives, as well as the need for a higher-end RAID card to connect it all together.

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No, your understanding is the same as mine. I would go with the smaller drives any time of the day since as you rightly put, you will get a much bigger benefit from the speed aspect of things. Just make sure that when you RAID 0 SSD's then TRIM etc does not always work so you may need to cleanwipe the drives every now and again. Apart from that, I would personally have opted for 8x128GB drives instead of 4x256GB since then you can even get more speed, plus chances are the RAID controller you've opted for will be able to handle 8 drives as well.

My 2 cents on the matter.

Thanks! The idea is to use the Plextor M5 Pro drives so I don't have to worry about TRIM. I'm really hoping I don't have to clean wipe the drives periodically....that would be a bit of a hassle as these are going into a server that can't go down too often.

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I think going for four drives would be the best overall move, although I would be hesitant to move to 8 128GB drives instead. While you might see even greater performance, the cost of the system will rise, with the additional drive bay requirements, cooling around the mass of drives, as well as the need for a higher-end RAID card to connect it all together.

Thanks for the guidance....much appreciated!

BTW, I sent you a PM on a different subject a day or two ago....I'm guessing you may not have noticed the notification.

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I think if you align the stripe size to the erase-block size of the SSDs, that (the RAID10) does sound good.

Normally for spinning disks, I'd blather on a bit about how a 4-disk stripe can actually be slower than a 2-disk mirror for some workloads (random reads with an IO size greater than the stripe size but less than the full stripe-width), but for SSDs I think it's a moot point.

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