half the performance in raid 1 array....

Using hdtune and crystaldisk as benchmkarks on my system i get half the speed if my disks are in raid 1. I made them non-raid disks and they doubled in speed. This is using alienwares raid drivers and all. Is this why raid 1 array is not offered in thei configurator page? I thought raid 1 would run as fast as single drive.....

 

I would more or less expect raid-1 to perform at Speed of a single drive. Assume 500MB/Sec to make it easier.

Read performance should be roughly 2 * 500MB/s (excluding sata 3/6 issues), while Write Performance should in theory be 1 * 500MB/s - Overhead of mirroring to second drive.

So I would expect around lets say 460-480ish on writes worse case, and 900+ on reads.

Also: Check the speeds in Atto Download ATTO Disk Benchmark v2.34 | techPowerUp

I have noticed discrepancies in hdtune/crystal.

 

In RAID 1 your system writes the same info to each disk. So it writes it twice, which explains the decrease in performance by 50%. Though it is like creating a real time backup so if one disk fails, you have an exact duplicate.

 

raid 1 is not stripe. it should not affect disk performance.

 

Raid 1 is mirror, thus it will affect performance.

 

no it really should not. i had a desktop raid 1 array with 1TB samsung drives and evga x58 sli board running them in onboard intel raid. their performance was not cut in half like the m18x is displaying. something is fishy. i am wondering if the dell intel drivers are at fault..

 

You might be running into the sata 3/6 flip flop.

Raid 1 performance: (Identical Disks 500mb/s)

Writes: 1 * 500mb/s - overhead.
Reads: N * 500mb/s (where N = number of disks).

If you're not seeing something similar to this definitely monitor the sata 3/6 of the devices.

 

how would i monitor this?

 

Raid 1 most definitely affects writes performance depending on the controller(shouldn't be half though) I actually agree that your mirrored drive may be running at sata2 speed, check with IRS tool

 

i should have clarified that i am using WD 750gb scorpio drives so they are sata 2.

intel raid storage says both drives are at 3.0BG/s speeds so that should be sata 2.

 

OK that's not so bad then, that eliminates the weird sata 3/6 issues between the two ports.

Do you have a crystal disk before and after or the numbers at least?

Edit: Another thought, one of the sata ports might have a hardware issue. Have you tested both drives individually outside of a raid volume (however you want to call it). Just wondering if the two ports have identical performance. Port 1 was dead/had issues on mine.

 

Yes with raid crystaldisk benched 45 read and 87 write. In non-raid it was 97 read and write.

 

The write performance definitely makes sense due to overhead the read doesn't make any sense whatsoever. I would expect roughly 160ish since it will read from both drives (similar to what a stripe would do).

Is this on each drive? or did you only bench one? ie see my previous edit.

 

The tests prove that it does affect disk performance on this platform. Keep in mind its software raid and not hardware raid.

 

doesn't matter if it's software raid. i had the same raid in the desktop evga x58 sli motherboard and it did not kill performance like this.

 

Mmm, yeah, Software vs. Hardware RAID doesn't take a big performance hit unless you are doing RAID-5, where XOR parity calculations are done on every bit of data written to the drive. Other RAID levels should be very close in performance.

I speak from experience, having done comparisons of a 4x SSD RAID on my desktop machine some years back, and comparing ICH9 vs. an Areca RAID controller with a hardware parity engine. In some rare cases the ICH9 software RAID actually managed to outpace the hardware RAID, most likely due to software RAID having access to the full complement of system RAM for use as a cache, while the hardware RAID has a dedicated DIMM for cache operations, limiting it's size.

 

Here's what I would do
(1) Test both disk(s) in crystal disk to rule out drive differences (internally if the same skip (2))
(2) If you have access to a usb 3.0 enclosure test both drives in that (if both are the same it will be a sata port/mb issue).
(3) Check raid drivers, you said you have intel RST, you using an older, newest, somewhere in between version of the raid driver?
(4) Bios update, if running on an older bios (not sure if you're running A03 etc).