[SOLVED] Slow performance from my DELL PERC 6/i card

[_deXter_]

Hi all,

For the purpose of experimentation, I have set up a RAID0 array of 4x WD7500BPKT drives. According to benchmarks, each WD in itself should have around 120MB/s read/write speeds. Even if you take overhead into consideration, I would expect at least 100MB/s for the outer-regions, so an overall RAID0 speed of 400MB/s is a fairly realistic amount, right? However, according to CrystalDiskMark, my array consistently scores around 190MB/s - which is really what I'd expect from two drives, but not four!

My stripe size is 64K and cluster size is 4K.
Read-ahead has been disabled as per Dell's recommendations for RAID0.
Write-back cache has been enabled.
Firmware is the latest version (6.3.3).
Card is actively cooled by a ~60mm fan running at ~4300RPM
Motherboard is ASUS P8Z77V-Pro, with a 3770K running at stock clock.
Card is installed in the black PCIe slot, which *should* be x16, but I'm not 100% sure.
I have an ATI HD 5970 on the blue x16 slot.
OS is Windows 8 Enterprise edition x64 .
I have two disks each connected on each of the SAS ports.
Partition is single GPT created under Windows 8, so they should be aligned properly - although I'm not sure how alignment comes into the picture with a RAID array; the drives are advanced format drives, and WD does recommend using their program to format the drive so that they are aligned properly, but again, I'm not sure if this would even work with a RAID volume.
SAS<->SATA cables are band new, so are the drives.
The drives themselves check out fine, no SMART errors to report.

My guesses are either 1) inefficient cluster/stripe sizes 2) alignment issues 3) PCIe slot running in x4 mode 4) Card is not capable of higher speeds? (unlikely though).

Would appreciate your thoughts, and maybe tips on how performance could be improved further, or perhaps even recommendations for a card that performs better, in the same price range.

Thanks!

 

[ingtar33]

the pci-e port speeds are so much faster then your SATA port speeds it isn't that. \believe me this, your WD Scorpio Black hard drives aren't fast enough to saturate a sata I port; so it isn't your pci-e port. (pci-e is a much faster interface then SATA)

I think your problem is your math stinks on how fast your WD drives should be. no 4 WD Scorpio Black hard drives will ever come close to 400 mb/s read/write in RAID0.

4 velociraptors wouldn't even manage that.

I'd be happy with 200mb/s; that's much faster then i would have guessed you'd get out of those 4 hds.

 

[popatim]

What did you use to test with? What settings?

 

[_deXter_]

the pci-e port speeds are so much faster then your SATA port speeds it isn't that. \believe me this, your WD Scorpio Black hard drives aren't fast enough to saturate a sata I port; so it isn't your pci-e port. (pci-e is a much faster interface then SATA)

I think your problem is your math stinks on how fast your WD drives should be. no 4 WD Scorpio Black hard drives will ever come close to 400 mb/s read/write in RAID0.

4 velociraptors wouldn't even manage that.

I'd be happy with 200mb/s; that's much faster then i would have guessed you'd get out of those 4 hds.

My math doesn't stink. The theory just doesn't add up. Something's obviously wrong somewhere.
I mean, it's well known that read/write performance of a RAID0 is nX where n= number of drives and X=Read/Write speed. Indeed, this is confirmed by me on my very own system where I get over 1000+ MB/s with my two of my SSDs in RAID0, using the onboard Intel controller.

As for the WDs, they have each been benched at 120MB/s, even right here at tom's and other sites too. http://www.tomshardware.com/reviews/advanced-format-1tb-hard-drive,3046-8.html
I can confirm I have the exact same model number, in fact, I purchased them specifically after going thru these benchmarks.

So according to raw math, 120x4 = 480MB/s but since we don't live in a perfect world, like I said I'm happy with 400 or even 350. But 190 is just not acceptable. I refuse to believe that the fastest 2.5" (laptop) harddrive in the market out there can perform so poorly. 190 isn't even in the ballpark range of the theoretical throughput. I understand that practical throughput varies with these things, but it's always within a sane range.

What did you use to test with? What settings?

CrystalDiskMark 3.0.2 x64 , sequential speed test, 3x 500MB, random data.
With HD Tune 2.55, I get an even lower figure - 125MB/s!

Something is really wrong here.

 

[_deXter_]

Solved it! It was the PCIe slot indeed! I'm now getting 629.1 MB/s read and 454.9 MB/s write. So much for "aren't fast enough to saturate a sata I port; so it isn't your pci-e port" and "no 4 WD Scorpio Black hard drives will ever come close to 400 mb/s read/write in RAID0"!

 

[ingtar33]

my apologies. i would like to know how you fixed it for future reference.

 

[_deXter_]

my apologies. i would like to know how you fixed it for future reference.

Oh, it was basically the PCIe slot, turned out the black slot is indeed an x4 slot. Put it in the blue one and its all good now. (The PERC 6/i is an x8 card.)

Appreciate your help though.

 

[ingtar33]

my apologies. i would like to know how you fixed it for future reference.

Oh, it was basically the PCIe slot, turned out the black slot is indeed an x4 slot. Put it in the blue one and its all good now. (The PERC 6/i is an x8 card.)

Appreciate your help though.

ah... you had it in a pci-e 1.0 x4 yeah... that would definately overwhelm that interface.

sorry i missunderstood you, i thought you were plugging into a pci-e 2.0 x8 or x16... that said i'm not sure my advice would have been different even if i had realized it was a pci-e 2.0 x4... i thought that format had more bandwidth then that.

live and learn :\