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It seems that SSDs inherently address things that RAID arrays were made to solve -

Seek time is 0 ; Lifespan is much longer / health reporting is better / data recovery is generally easier.

Plus, when I was looking for where someone may've already asked this - I see a handful of questions where people are complaining that RAID makes their SSD's slower -

So why might you still use a RAID with SSDs - ? -

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    RAID wasn't created for any of the reasons you stated. It was created to provide redundancy (or resiliency as Chopper3 and Massimo stated in their answers). If your idea of resiliency is data recovery then you're doing it wrong.
    – joeqwerty
    Aug 20, 2015 at 15:49
  • Need? No. Useful? Yes. Exactly like for HDDs.
    – Massimo
    Aug 20, 2015 at 15:54
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    I'm voting to close this question as off-topic because the premise of the question is utterly misguided. RAID was created for redundancy, everything else is just a byproduct.
    – kasperd
    Aug 21, 2015 at 9:27

2 Answers 2

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Two main reasons:

  • Resilience. Yes, they are fast. And they are self-repairing (to some extent). But they still can and will fail. And when they do, you'll be glad you used RAID (and backups, of course).
  • Size. SSDs are generally quite small compared to HDDs, and anyway even with HDDs you still need to RAID several of them in order to build serious volumes.

And, as an additional reason:

  • Speed. Yes, speed too. A bunch of disks operating in parallel (RAID 0, 1, 10) will always be faster than a single disk, no matter the storage technology in use.
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  • AH, Size - that's an important one I hadn't thought of - - - Thanks, good answer!
    – rm-vanda
    Aug 20, 2015 at 16:01
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Resilience - turns out you can't just put a one word answer.

Edit - actually let's answer your misconceptions.

No SSD's don't inherently address all things, they're quicker yes, that's it - we still need resilience. I've been using PCI-based storage for nearly a decade (FusionIO) but always in R1 as we need the resilience.

Seek time isn't actually zero, page table changes still take time, not long but they do.

Lifespan really is NOT 'much longer' - in fact in many scenarios they're STILL worse.

And some systems, especially when misconfigured, can make SSDs slower - but not if the right products are combined and people do their homework.

Also SATA/SAS SSDs are pretty much over - for laptops/desktops you should be buying M.2 PCIe-based storage and for top-end/commercial kit you should be buying NVMe kit - SSDs have had their best days, move on.

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  • Not sure about the last comment, most laptops/desktops only have M.2 SATA, there is considerably less selection than regular SATA drives and most of all its not a very user friendly package, just like PCIe card drives. In servers people need to be able to hotswap on failure. So a bit early to pronounce on SATA/SAS without a viable alternative in the picture.
    – JamesRyan
    Aug 20, 2015 at 16:38
  • Oh I still love SAS but there's going to be a HUGE shift to M.2 PCIe as almost all new Skylake based machines will have a slot on their motherboards and they're the same price & smaller. Oh and you can hotswap NVMe if your system/OS supports.
    – Chopper3
    Aug 20, 2015 at 17:04

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