Solved Help me with this Server Purchase (beginner in server hardware) regarding RAID ?
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LVM does not provide RAID. LVM rides on top of RAID (or vice versa) and recently they have integrated MD management into LVM so that it can appear that you have RAID inside of it, but it is still MD handling the RAID. On Linux you have MD, ZFS and BtrFS RAID options. But ZFS is not available on the better platforms and is extremely new on Linux in an enterprise way, so probably not best unless really needed and is dramatically overhyped in general and isn't designed to be fast. BtrFS is super new and fine as a general filesystem but advanced features on it are pretty experimental. MD is what we've used for decades.
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What hypervisor are you considering? VMware ESXi cannot use software RAID. Hyper-V can but nothing enterprise or production ready.
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KVM
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Got it, I just saw BTRFS in Centos installation option and been playing with it but in my lab and not production.
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@scottalanmiller said in Help me with this Server Purchase (beginner in server hardware) regarding RAID ?:
MD RAID
People rave about the new features of BTRFS so I thought can I do it for a new production server in 2017, perhaps I thought by now we will have more people tested it.
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With KVM you'll want either MD RAID for software RAID or a good hardware RAID card. Those are really the two choices.
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Got it, many thanks.
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@msff-amman-Itofficer said in Help me with this Server Purchase (beginner in server hardware) regarding RAID ?:
@scottalanmiller said in Help me with this Server Purchase (beginner in server hardware) regarding RAID ?:
MD RAID
People rave about the new features of BTRFS so I thought can I do it for a new production server in 2017, perhaps I thought by now we will have more people tested it.
Yeah, people get excited about really inappropriate things. Make sure you read this...
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@scottalanmiller said in Help me with this Server Purchase (beginner in server hardware) regarding RAID ?:
With KVM you'll want either MD RAID for software RAID or a good hardware RAID card. Those are really the two choices.
No, the correct answer is that unless you are already intimately familiar with software RAID and your company will be able to easily replace you with someone else that can handle software RAID, you do not use software RAID.
It is nice and shiny and bullet proof, to those that know it. Generally there are zero viable use cases in the SMB market for it. The fact that you even asked the question means buy a hardware RAID card.
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Jared is correct, this is an "if you have to ask" scenario. Software RAID requires extra knowledge and support capabilities and an IT staff that all understand how to react to it. You lose capabilities like blind swapping that are really important for SMBs to be able to change out staff and use consultants.
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@scottalanmiller said in Help me with this Server Purchase (beginner in server hardware) regarding RAID ?:
like bland swapping
hahahahaha
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The selection of a RAID controller is one the most important parts when configuring a server. In no way a software RAID will be as fast as a hardware RAID and its model is greatly dependent on the amount of disks you will be using. It would be much easier to provide provide you with a specific model if you would provide us with the amount of disks(type) you are planing to use.
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@DimS said in Help me with this Server Purchase (beginner in server hardware) regarding RAID ?:
In no way a software RAID will be as fast as a hardware RAID ....
Actually that changed with the Pentium IIIs processors circa 2000. The extra CPU power on the mainboard, on average, became overwhelming to the RAID offload CPUs in that year. Since 2000, the average server is faster with software RAID than with hardware RAID and the gap has widened every year since that time as mainline CPUs have gotten faster and faster with more and more spare overhead. The idea that hardware RAID can compete in speed is a 1990s idea from a time when the central CPUs were barely more powerful than the RAID controllers and were extremely taxed all of the time. Today the excess overhead in nearly all systems is so extreme that RAID cards can't compete. And you can put dramatically more cache on the main CPU than on the RAID card as well. Most RAID cards max out at 2GB RAM cache today, while I personally have software RAID customers with 128GB RAM cache, for example.
There are still edge cases where hardware RAID remains competitive in terms of speed, but these are increasingly rare and I'm not sure that I've ever seen one in person. Hardware RAID just doesn't have the resources to compete.
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More importantly, though, is that RAID is not normally constrained by CPU and looking at any RAID implementation for speed is not a good way to think about it. Cache size matters, yes. Easy of use, reliability, clear understanding... these are highly valuable in nearly all cases. Choosing RAID level for speed, that matters potentially a lot. But the RAID implementation really doesn't. ZFS RAID 5, MD RAID 5, Adaptec RAID 5, LSI RAID 5... all so close in performance that it just doesn't matter in the real world, especially not to an SMB.
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@msff-amman-Itofficer said in Help me with this Server Purchase (beginner in server hardware) regarding RAID ?:
@scottalanmiller said in Help me with this Server Purchase (beginner in server hardware) regarding RAID ?:
MD RAID
People rave about the new features of BTRFS so I thought can I do it for a new production server in 2017, perhaps I thought by now we will have more people tested it.
They sure do. Phoronix over the weekend: Btrfs Getting RAID 5/6 Fixes In Linux 4.12 Kernel
