SSD Raid options

I am in the midst of a Pre-Legion PC upgrade.

Here's my current system

Intel i7 4790k
Gigabyte Z97 MX Gaming 5
16GB G.Skill DDR3
Gigabyte GTX 970
2x 250GB Samsung 840 EVO
40" 4k monitor

Switching to

Intel i7 6800k
ASRock FATAL1TY X99m killer/3.1
32gb Kingston Hyperx Fury DDR4
ASUS Strix GTX 1080
?? SSD
40" 4k monitor

I have a bunch of random SSDs lying around, so I got plenty of options. First is just to move over my existing SSDs and call it a day.

I'm nervous to keep using RAID0. Haven't been burned yet, but I feel like it's a ticking timebomb. I am considering a RAID 10 with 2 more 250gb EVOs, which gives me the same capacity, roughly the same write speeds, but probably faster read speeds.

Should I just get 4 fresh drives ($$$$) or just get 2 and add to what I got? I also have a 500GB 850 EVO, so I could just get another of those and RAID 1, but I've heard about IO stutter with multiple instances of wow reading off a single SSD (which may be mitigated by the RAID 1, who knows?)


EDIT: I should note that my current system works fine for 5 boxing but am going to try about 8 boxing, with pretty high settings, I just want a bit more headroom for other stuff, (Youtube stutters when playing for instance)

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Originally Posted by daviddoran

I am in the midst of a Pre-Legion PC upgrade.

Here's my current system

Intel i7 4790k
Gigabyte Z97 MX Gaming 5
16GB G.Skill DDR3
Gigabyte GTX 970
2x 250GB Samsung 840 EVO
40" 4k monitor

Switching to

Intel i7 6800k
ASRock FATAL1TY X99m killer/3.1
32gb Kingston Hyperx Fury DDR4
ASUS Strix GTX 1080
?? SSD
40" 4k monitor

I have a bunch of random SSDs lying around, so I got plenty of options. First is just to move over my existing SSDs and call it a day.

I'm nervous to keep using RAID0. Haven't been burned yet, but I feel like it's a ticking timebomb. I am considering a RAID 10 with 2 more 250gb EVOs, which gives me the same capacity, roughly the same write speeds, but probably faster read speeds.

Should I just get 4 fresh drives ($$$$) or just get 2 and add to what I got? I also have a 500GB 850 EVO, so I could just get another of those and RAID 1, but I've heard about IO stutter with multiple instances of wow reading off a single SSD (which may be mitigated by the RAID 1, who knows?)


EDIT: I should note that my current system works fine for 5 boxing but am going to try about 8 boxing, with pretty high settings, I just want a bit more headroom for other stuff, (Youtube stutters when playing for instance)

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8-boxing won't really stress the drives any more than 5-boxing, with the possible exception of hearthing/porting to a major cap city that has a ton of people in it.

I was running 2x 840 Pros in RAID 0 and getting about 1GB sequential read/write. It was very easy to set up. I'm now on 2x 950 Pro PCI-E M.2 drives in RAID 0 (with special BIOS support) and while it works, there are some early-adopter quirks that make installing/upgrading OS (e.g. from Win7 legacy to Win10 UEFI) a pain in the ass. Granted, having ~2.5GB read speeds makes booting/loading games stupid fast, I'm about burned out enough on OS reinstalls that I'd tell my old self to just pick up two 850 EVO drives and put them in RAID 10 with the 840 Pros and call it a day, assuming your board supports it.

The increase in performance with a single M2 PCIe3 x4 SSD can be well in excess of using a RAID 0 pair of 840/850's; max sequential stats anyway, random loads can be variable, especially writes (applies to all disks of all types), but generally the M2 will just kick butt regardless.

Your idea of faster read speed of a RAID10 over a RAID0 is incorrect. RAID10 very rarely speeds up reads over a RAID0 of 1/2 the number of disks, despite having pairs with the same data, because the controllers just don't read data like that (not the usual ones anyway, although interestingly enough a Windows software RAID does and a couple of Unix flavours do too, a few hardware solutions can aswell, although they are usually rather expensive), and even if they did, the southbridge would likely be flooded (you've not mentioned a RAID controller so I figure you're going with the onboard).
RAIDs are not primarily designed for performance (despite the premise behind a RAID0), and the focus that is put on it when designing them. Redundancy is the aim, which is why it is in the name (although, as preached in many places, a RAID is not a substitute for a working backup strategy).
Using mixed drives your performance will be based off the level of the slowest performing drive in a RAID. Because the controller needs to wait for the slowest drive to finish it's action.

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but I've heard about IO stutter with multiple instances of wow reading off a single SSD

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This happens on mech disks too, and is usually resolved by having a second+ copy of the install, which points to it being a problem caused by games file access strategy (and potentially locking/blocking), rather than the disk i/o itself. Faster read i/o will help hide it, but it is just trying to hold your bumper on with some gaffer tape. If it was determined which files were under contention, they could be virtualised in ISBoxer (if you happen to be using that), and that would provide multiple copies of the affected files rather than replicating the whole install.


As for your YouTube stutters. That would point to a different problem again. While YouTube does cache locally, there is also a memory buffer to account for read I/o being delayed, so if there are stutters, either the cache is empty (and thus your link to the server is not wide enough - which is not necessarily the same as your connection to your ISP), or the buffer is not being filled fast enough, or your CPU is busy doing something else, and does not have the resources to decode the stream. The buffer not being filled from the cache is the least likely cause.

It's probably worth noting that in my testing (I'd say experience, but the amount of back and forth and try-this-then-try-that amounts to testing :p), the benefits of any striped RAID with SSDs is that you greatly improve the poor small-file-write performance. I've seen this have a dramatic effect on things like logging out of one group of toons and into another, or speeding up quick-saves in single-player games like Half Life, Shadow Warrior, etc. I had better write/save speeds with two 840 Pros than I did with a single 950 Pro.

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It's probably worth noting that in my testing (I'd say experience, but the amount of back and forth and try-this-then-try-that amounts to testing :p), the benefits of any striped RAID with SSDs is that you greatly improve the poor small-file-write performance. I've seen this have a dramatic effect on things like logging out of one group of toons and into another, or speeding up quick-saves in single-player games like Half Life, Shadow Warrior, etc. I had better write/save speeds with two 840 Pros than I did with a single 950 Pro.

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True. The majority of the time the disk I/o will be at a Queue Depth of 1, because you just wont be generating the workload to get higher, which means you will be at pretty much the lowest write performance for the SSD, and it will probably be 4k random writes, which is usually the lowest performing write type; although, ideally, you are running a block size that matches your stripe size, you have sized your stripe to the workload you are running**, and you have aligned the volumes correctly, as not doing so can significantly affect performance, and in some cases, defeat the purpose of striping data across disks.
** High performing RAIDs are effective for a given type of workload. It usually requires in depth knowledge about the services that you are hosting in the enterprise world where you are planning single task servers. Home systems are just a PITA with their multiple usage scenarios, and don't translate very well to a high performance RAID design. This is not to say a home system wont benefit from a stripe, it just wont be as effective.

So, yes, having 2 disks to write half the data to will always be faster, unless the single disk write random performance is faster. If it fairly simple enough to show this with some simple stats and easy math.
This is a simplistic view as chances are you are not really writing 4k writes all the time, it will vary depending on many factors, but it is easy to show the worst case scenario, and the improvement you get from it when using RAID0.

For eg.
an 840 PRO (256GB), has a random write @ 4k, of approximately 33000 IOP's,
an 850 EVO (250GB) , has a random write @ 4k, of approximately 40000 IOP's,
a 950 PRO (256GB), has a random write @ 4k, of approximately 57000 IOP's,

So two 850 EVO's in a raid 0 will have an effective comparable rate of 80000 IOP's, two 840 PROs 66000 IOP's, hence both are faster, for 4k random writes than a single 950 PRO.
Note: depends on firmware for the drives too, the 840 PRO's original firmware was around 15k IOP's @ 4k random writes.

Comes down to the problem you are trying to solve, and whether the solution is worth it, to you, for the money you need to spend.

RAID 0 is ticking timebomb.
RAID 1 = fast read, normal speed write.
RAID 10 = fast write, fast read.
BUT
Intel RST RAID 1/10 doen't support TRIM, what is the long term problem...

So if you want fast..but safe? one 950?

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Originally Posted by Lyonheart

So if you want fast..but safe? one 950?

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Sure, but you need the interface to use it. This requires either an m.2 slot on your motherboard (which will probably use up some PCIe lanes or shut down some SATA ports depending on what you are able to select in the BIOS), or a card with an m.2 interface which plugs into a PCIe slot. There are also different sized m.2 devices, so make sure that whatever your motherboard has, or whatever PCIe card you're looking to buy, is able to handle the Samsung 950 Pro. I forget exactly what size it is, but I think it's a 2280 or something like that (I'm too lazy to look it up right now).