Questions: PCIe, M.2 U.2, Mobos, Linux

[Frank_Rizzo]

A few questions if I may.

Looking at purchasing an M.2 / PCIe 250GB SSD to be used for database work (large files, 300MB-1GB in size). Rig will be

* New i5-6600K
* Z170
* 950 or 951
* HD5670 (it's not for gaming)
* Win 8.1 32bit and / or CentOS (64bit) or equivalent (Fedora)

M.2 or Adaptor?
It seems a PCIe adapator is faster than the M.2 port and yet some mobos state this:

1x Turbo M.2 32 Gb/s

Does that mean you can get the full 2000MB/s Read, 900MB/s Write from the M.2 port directly, and that there is no need for the adaptor card to get the fastest speed?

and then there is this beast:

"Twin Turbo M.2 64Gb/s + Turbo U.2 ready"

What is U.2? Are there drives that work with it now? How does twin turbo work? Does it require two drives?

If the M.2 is always slower than PCIe regardless of the above then is the ASUS and the Lycom identical in performance but one is cheaper?

Overprovisioning
Is that still required for these drives? Of the 256Gb only around 50Gb is actually used so plenty spare.

O/S
I understand the 950 is retail and thus has drivers to allow booting in Windows. Are there also drivers for Linux or would the 951 be more suitable?

Can these drives be set to dual boot?

Would it be easier all round to just use an 840 Evo as a boot device and run the 950 as the data drive?

 

[h4rm0ny]

M.2 and PCI-e SSDs are essentially the same (so long as you're not talking the old M.2 "SATA" which is obsolete). Chiefly, the physical connector is different, with the M.2 not having to be a big PCI-E card, which is pretty important if you want to put one in a laptop.

The reason you might see an M.2 be slower is because it might use only 2 PCI lanes, or be an old PCI gen. 2 instead of gen. 3. What you want to do is check your motherboard and see what it can support. if it says you can get 32Gb/s, then that's what you can get - the socket is hooked up to 4 PCI-E gen 3 lanes, so... enjoy!

U.2 is the new SATA Express. I know Intel do a U.2 version of their 750 SSD (I'm pretty certain that's not the version OCUK sell) but I think drives using it are still pretty rare. Maybe there are more in the enterprise market. I would, for the time being, forget about it. I've no idea how it's going to play out in the market.

Yes, over-provisioning slightly is still a good idea (but please correct me someone if there's been a development and it no longer makes a difference). However, as you note yourself, 150GB of over-provisioning is a little excessive.

I can't comment on the Linux drivers for the drive which is slightly embarrassing because I program on GNU/Linux professionally - but I also wont spend that much money on a new drive right now so I've never looked into it! I too work with databases and I envy what you're about to experience.

On the subject of database performance, btw, I don't know exactly what you're working with but there's a good chance random read and write speeds are going to be more significant to you than sequential. Certainly there are plenty of cases with database where sequential is critical. But a lot of the time it's all about the IOPS. Just a comment, really. What database are you working with? You mention Linux as an option so I'm guessing MySQL or Postgres.

Hope this is helpful. Answers are correct to the best of my knowledge. Hopefully someone would chime in if I'm in error anywhere, but I think you should be good.

 

[Frank_Rizzo]

Thanks for the info.

There are two rigs I am working on. One is a desktop running xBase type data. The other is a server running xBase and MariaDB.

The desktop data is mostly looping stuff, updating columns, It's single use so I don't think IOPS would be an issue here. Most of the data is copied to ramdrives anyway so it's more of finding the best drive / connection for the copying of data to and from RAM.

The server obviously is a different issue. I need reliability more than anything else as there will be multiple users at a time.

I doubt M.2 would suffice and being in a 1U I would be concerned about heat. The 750 looks ideal but I may go with a 950 pro on an adaptor card if space allows.

 

[h4rm0ny]

Thanks for the info.

There are two rigs I am working on. One is a desktop running xBase type data. The other is a server running xBase and MariaDB.

The desktop data is mostly looping stuff, updating columns, It's single use so I don't think IOPS would be an issue here. Most of the data is copied to ramdrives anyway so it's more of finding the best drive / connection for the copying of data to and from RAM.

The server obviously is a different issue. I need reliability more than anything else as there will be multiple users at a time.

I doubt M.2 would suffice and being in a 1U I would be concerned about heat. The 750 looks ideal but I may go with a 950 pro on an adaptor card if space allows.

Okay, well sounds like you have the desktop side sorted. Yes, if it's just copying data from RAMDISK, then sequential speeds are what you care about - you're right.

The second scenario is rack mount, then. Okay, that changes my answer a bit about U.2. I don't see it in the enthusiast market much if at all (and certainly not regular home users), but it does seem to be more of a thing in the enterprise market. I would at least look into this.

If this is a production environment then the only thing that will give you actual reliability is multiple disks. And more realistically, multiple servers with failover.

But on the Intel 750 vs. Samsung 950, I'd honestly be tempted to at least assess the 750. More expensive, admittedly. But random reads and writes are faster. If your server has plenty of RAM it will cache a lot of queries and table states. Updates are where you usually hit your bottlenecks. You say you're worried about heat, though and I believe the 950 sips less power.

Anyway, hope this is of help. I'm not sure exactly what your scenario is but there are some very large sites that run successfully even off HD, so unless you're doing something specialist, I would think either should be more than ample for your needs.

EDIT: Oh, you asked about drivers. Not my area especially but I know driver support for the 950 is more widespread than for the 951, given the former is retail orientated.

 

[Frank_Rizzo]

I got the desktop rig sorted.

It was a bit of a hassle to get Windows to install on the 950 Pro at first. I was using a Windows 8.0 DVD, which did not have the NVMe drivers for install time loading. In the end it was easier to just download the 8.1 install from Microsoft.

The device works great and hits the manufacturer's stated speeds.