How should I determine exact over-provisioning levels for 1TB Samsung 850 Pro SSDs to be used in a Raid 10?
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First thing... welcome to the community! Great to see new faces.
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@creayt said:
- Hardware raid controllers don't support TRIM.
This is generally true, but nothing makes this true other than controllers not being up to date yet.
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@scottalanmiller Thanks, liking the site so far
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Intel had TRIM on a controller back in 2012. But who wants an Intel controller. Avoid those, just a point of interest that it does exist sometimes.
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I've not done this, but what you are proposing should be exactly what you do for the situation. TRIM isn't important on an LSI controller because you manually under-provision the space on the drive (or over-provision your purchasing, however you want to look at it.)
http://serverfault.com/questions/654025/trim-support-in-hardware-raid-perc-h700
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Curious to see how this plays out, keep us updated!
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@scottalanmiller Interesting. The approach in that link seems to be different than what I've read elsewhere, which is that you set overprovisioning on each SSD before adding them to a virtual disk ( array ), and that each drive will use that allotment internally to maximize its individual performance and longevity. The result being that each drive shows a lower capacity available for the virtual disk use before you create it. That link seemed to say "leave some of the total, available-to-the-virtual-disk-itself capacity unused as part of the virtual disk assembly", which to me seems like it implies that the raid controller itself will somehow maneuver that unused pool of space, unless doing so just means the drives will, but it seems like if you do it at the virtual disk level how can you be sure the unused portion would be split across all drives evenly, and not just be the last drive or so of the array? I'm new to servers and learning stuff at every sentence, so the way I'm seeing this might be off.
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I think your idea makes more sense. Limit was is provisioned on a disk by disk level if the option is available to you. Otherwise, the controller is smarter than we assume that it is.
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@xByteSean and co., would be interested to get your feedback on this too if you have any. Thanks!
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So I'm still at a loss for this but am going to deploy these SSDs in the next few days. @scottalanmiller , what do you think of over-provisioning them such that 20 or 25% of the full capacity is reserved per drive? Is that heinous ovekill?
The workload will be Windows Server 2012 R2, IIS, MySQL, and a J2EE app server, running for the most part a single application. Thanks.
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20% is a lot, but not crazy overkill. I might taper that back to 15% myself. But if that gives you enough capacity for your needs, go for it.
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@scottalanmiller said:
20% is a lot, but not crazy overkill. I might taper that back to 15% myself. But if that gives you enough capacity for your needs, go for it.
Sounds good to me. And I believe the RAID controller supports online modification so I could theoretically add another 4 1TB drives to the 10 later if/when I need it. Thanks for your help, much appreciated.
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Drives are deployed. Benchmarks attached.
The left is a Raid 10 of 10K 6 Gbps SAS drives, to the right is the Raid 10 of 6 Gbps SSDs. Thanks to everyone for the help.
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And that is just througput, measure the IOPS for the BIG increase!!
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@scottalanmiller Good call. Can you suggest a good tool to do that with?
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@creayt said:
@scottalanmiller Good call. Can you suggest a good tool to do that with?
http://community.spiceworks.com/topic/314145-what-is-the-best-i-o-iops-testing-tool-out-there
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@thecreativeone91 said:
@creayt said:
@scottalanmiller Good call. Can you suggest a good tool to do that with?
http://community.spiceworks.com/topic/314145-what-is-the-best-i-o-iops-testing-tool-out-there
That's what I found last night, installed it, tried to run something obvious but it looks like it requires a bit of an investment in setting up testing. Was hoping for something a little bit simpler to just plug and play, but I can definitely dig into it when I get some downtime. Thx.
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