My RAID woes continue...

A few months ago, I wrote about wondering why my RAID-0 performance... to put it bluntly, sucked. I got slower than 1 Vertex 4 without RAID. One of the problems was I had two different drive types (Samsung 830 (Dell) and Samsung 840 PRO), well to cut a long story short, one of the drives died (I had backups so all is good, I understand drives can sometimes die). So now I have two 840 PROs in RAID-0, and they're both from different batches, and both not from Dell...

However, again, upon a fresh install, I ran AS-SSD just to check how my new setup was handling, and WHAT IS THIS?! 480 MB/s read, 456 MB/s write (sequential), that's garbage. That's less than the theoretical max of ONE drive (and less than my desktop gets on a single 256 GB Vertex 4...

So I thought, hmmm, let's have a poke around the settings (FYI: I'm using 16K Stripe Size, My desktop is using 32K Stripe Size). I found that disabling Windows Cache Flushing and enabling the Intel Writeback Cache apparently improves performance... WRONG! It made my write performance EVEN LOWER... 431 MB/s now. GREAT!

Idly, I was browsing around the settings to find something to change (there isn't much though, don't you love software RAID), but I found this...


>SATA transfer rate: 3 Gb/s... ey? That's not right, Port 1 should also be 6 Gb/s... I looked around on the Alienware Support site and sure enough (according to: Alienware M18x R2 Sata 3 Ports available), Port 1 and 3 on the drive caddy are SATA III (6 Gb/s)... exactly where my drives are. The middle one (Port 2) is my data drive and has never been moved.

The other drive (Data drive, 5400 RPM HDD) is also showing 3 Gb/s, and my ATAPI drive (Bluray) is showing 1.5 Gb/s...
So right now... I'm getting 1 x SATA III, 2 x SATA II, and 1 x SATA ... I and a half?

Where has my other magical SATA III disappeared to... I'm also using RST 11.7 Driver (latest I could find).

I've tried a bewildering array of benchmark programs, all pointing to the same sub 500 MB/s performance.

Are there any suggestions to what this could be?

 

Would you be willing to delete the RAID 0 array, install Windows 7 in Raid 1 and using the IRST create a RAID 0 array with either a 64K stripe size or 128K.I had the same problem with 2x Vertex 4 in RAID 0(one of the drives showing up as 3GBs) and very poor write speeds, untill I did what I suggested;and as a side note I find that the IRST driver 11.6.0.1030 performs better than the 11.7.Also you should have "Enable write caching" checked but don't check"Turn off Windows write-cache buffer flushing" This solved my problem, I hope it helps you.

 

I'm not sure I follow you. What does RAID-1 have to do with it?

Thanks. I am trying a 64K stripe size now and installing a 11.6

 

Do you have Windows 7 installed on your rig now? Is it in RAID 0 with a 16K stripe?

 

No I reinstalled. Its Raid 0 with a 64K stripe

 

What I meant in my 1st post was when I was having problems similiar to yours, I entered the RAID configuration and deleted the RAID 0 array and then created a RAID 1 array,installed Windows 7 and then downloaded the IRST and using that configured a RAID 0 array with a 64K stripe size,waited about 45 minutes while the program migrated the data.When that was completed I was able to extend the unallocated space on one drive into 1 big drive.

 

I tried running a benchmark other than AS-SSD (CrystalDiskMark) and I got 1077 MB/s read but only 460 MB/s write. And most of the time the benchmark would freeze and the entire system locks up and I need to force shutdown with power button... yay for Alienware. I should have gone for Clevo.

 

The problem is your SATA interposer. Alienware needs to replace it for you. It's a common problem that SSD run at SATA2 instead of SATA3 speed when that part is not functioning correctly, and that may have been the trouble all along with slow performance. So, please don't go get a plastic Clevo with a crippled BIOS on account of a $35 part that can be replaced in 10-15 minutes. I think you might end up regretting that.

 

After using 11.6 Driver, they both show as 6 Gbps. However my write performance hasn't increased, nor has the fact that the benchmark crashes and stalls the entire system to a point where I need to force power off (only on the write test)

 

I still think you have a bad SATA interposer cable. If not that, then one of the drives is goofed up... but more likely the cable.

 

Just wondering, although the interposer is likely the culprit, do both of your drives have the same firmware? - it's not likely to make a HUGE difference but if they ARE different, might be worth seeing if you can get them both on the same revision.