Lower IOPS in RAID 0 (AMD 990FX)

[ksantangelo23]

Hello, I have an issue with two of my Samsung EVOs, both 250 GB in RAID 0.

As a single drive, each one performs normally - the read and writes are great, my computer is snappy and it performs as expected in Samsung Magician benchmarks. The problem is when I attempt to put them in RAID 0, the performance is horrible (given these are two SSD’s) for all benchmarks except for sequential read/write.

The IOPS for R/W drop to the 30-40K range, even rebooting and shutting down on a fresh Windows 8 install is takes noticeably longer.

I’ve tried nearly everything, all the solutions I’ve found online to similar issues don’t seem to apply to my set up. Here are my relevant specs and what I’ve tried:

- MSI 990FX-GD65 V2 (latest firmware), six SATA ports, ALL 6 GB/s
- AMD 8350 CPU
- Two Samsung EVO 250 GB - both new and perform to specification individually

Things I confirmed are:
- AHCI drivers manually installed
- Disconnected all other drives, including external
- BIOS reading SSD’s as SATA 6GB/s mode
- Consecutive ports (tried SATA slots 1+2, 3+4, and 5+6 and 1+6 out of frustration)
- Attempted both UEFI RAID-0 set up and AMD’s onboard (Ctrl+F) RAID setup

I’m completely out of ideas, any support would be appreciated! Thanks in advance

 

[dave_the_nerd]

It's probably your RAID controller. *shrug*

Keeping track of that stuff is hard work. Motherboard RAID is usually not-super-fast-and-awesome.

 

[ksantangelo23]

It's probably your RAID controller. *shrug*

Keeping track of that stuff is hard work. Motherboard RAID is usually not-super-fast-and-awesome.

At this point, im almost ready to give up and purchase a RAID card but dont know where to start for that, I've always used onboard RAID without a problem. :hmm:

I'd only want buy a RAID card if my onboard RAID controller really is unable to be resolved, which I cant really imagine.

 

[Squeetard]

I'm leaning towards the controller being slow as well.

 

[ksantangelo23]

I'm leaning towards the controller being slow as well.

Ok, are we thinking about a defect, or a setting is wrong?

 

[dave_the_nerd]

Ok, are we thinking about a defect, or a setting is wrong?

Neither.

It's not that there's something wrong with your RAID controller. It's just that with the extra RAID magic you're asking it to do, it's maxed out at 30-40k IOPS. (Whereas when it doesn't have to do that extra work, it can devote more resources to IOPS, thus getting higher scores out of a single drive.)

I mean, you'd have to get some reference points to be absolutely sure, but that's my bet.

Manufacturers cut corners. Remember the X58 boards, with the ubiquitous Marvell SATA-3 controllers that were slower than the Intel SATA-2 controllers on the same motherboards?

All that aside, you're running RAID-0 with consumer SSDs. If you're benchmark-pimping, which seems likely, don't drop hundreds of dollars on a RAID controller just for that. (Get a new GPU instead!)

 

[ksantangelo23]

I appreciate the reply, but I find it hard to believe that it’s intended that my RAID controller would limit itself to the point of performing worse than a single drive. I’m sure there are outliers as you mentioned, but my board, SB and chipset are mainstream and generally well-reviewed.

 

[dave_the_nerd]

I appreciate the reply, but I find it hard to believe that it’s intended that my RAID controller would limit itself to the point of performing worse than a single drive. I’m sure there are outliers as you mentioned, but my board, SB and chipset are mainstream and generally well-reviewed.

That's like saying, "What? My car can't have a hard upper limit on its speed, it's a BMW!"

Here's a review showing SSD RAID scaling with the 990FX.

On the jump from 1 to 2 drives, you can already see 4k writes dropping and seek time increasing. And pretty much every measurement has a ceiling where adding additional drives doesn't help.

With faster individual drives like the 840 EVO, you just hit the limits of the RAID controller faster.

 

[ksantangelo23]

I understand limits, and I came across this link as well.

But my drop in IOPS into the 30-40k range is still not accounted for. I'm still confused.

 

[G73S]

when I called Samsung they recommended me NOT to RAID my Samsung 840 1TB Evos and told me to use RAPID.

I benchmarked both, and found RAPID to be better slightly in lose in a few other areas, but in the real world usage, you will not notice a bit of a difference neither in boot times nor in app launch times between RAID and RAPID. So save your diskpace, and reinstall Windows in AHCI mode and enable RAPID on your OS drive

 

[dave_the_nerd]

I understand limits, and I came across this link as well.

But my drop in IOPS into the 30-40k range is still not accounted for. I'm still confused.

What's to be confused about?

Your RAID controller can, under normal circumstances, throw X IOPS at a single drive.

However, the extra time and attention it takes to drive multiple disks at the same time in RAID-0 means it can only throw <X IOPS at the array.

 

[TerryMathews]

What's to be confused about?

Your RAID controller can, under normal circumstances, throw X IOPS at a single drive.

However, the extra time and attention it takes to drive multiple disks at the same time in RAID-0 means it can only throw <X IOPS at the array.

This. Taking that block, splitting it into you and writing it to 2 different drive is not a free operation.