Weird RAID Benchmarks

[Qafyg]

Anyone has any idea what could cause the sudden drops to near 0 MB/s.
Raid6 - 64k Stripes - 512k Sectors - WBC Enabled
8 Samsung F4 2TB

Computer is freshly installed nothing is running on the array.

It happens when I configure HDTune for any block size. Here are a sample with 4k and 1MB. It also happens when I write to the array with WBC or without.

HD Tune 1MB Block Size:

HD Tune 4k Block Size:

HD Tune 8MB Block Size:

 

[sub.mesa]

First of all, do not use HDTune for RAIDs; you get weird performance issues which do not occur in real life when using a filesystem instead. So instead use CrystalDiskMark or AS SSD.

But the drops you see are likely because this is your system drive, and thus any background systemdisk I/O will lower the performance of your RAID array used for other stuff. That's why ideally you should have an SSD for system drive, so that any other HDD in your system won't be burdened with system disk I/O accesses on the background.

Oh and your sectors are 512 bytes (512B); not 512 kilobytes. A sector is the smallest unit, kind of like the 'atom' in its original meaning (indivisible).

 

[parityboy]

@OP

1) Is your OS on this array or on a separate drive?

2) Did you update the firmware on the Samsungs? This is a necessary step.

 

[Qafyg]

Thanks for the heads up about HDTune, I didn't know it wasnt reliable for raids.

My OS is on another single drive, at the time there wasn't even a partition created on the array. I got the same behavior after I formatted a partition though.

Firmware was update on all 8 samsungs.

It's weird because I have my case open next to me on my desk and I can almost hear the drives make a different seeking noise (like there's more activity) when the MB/s drops to zero. I'll run more bench with the other programs to see if I have different results.