I have the following system:
- ASUS Z97-WS motherboard
- Intel i7-4790K (not overclocked)
- 16GB 1833MHz memory
- USB 3 external disk docking station (BlacX 5G Duet)
I use the docking station to swap out backup disks on a regular basis. During a normal backup or archive operation, this is rock solid and very fast. I'm quite pleased with performance.
Retrospect has a "media verify" option, during which the program does the following:
- reads every file from the backup or archive to ensure the file can be read successfully
- If the file also exists in its original location on the source being backed up, it calculates an MD5 hash and compares it to the hash stored in the catalog
A "media verify" is read-intensive, reading about 100MB/second. With the docking station connected to one of the Intel USB3 ports, the disk will disconnect after reading 20-30 GB or about 5 minutes of continuous high read-only load, and then immediately reconnect. If watching in Windows Explorer the drive disappears and reappears within about 10 seconds. I have tested with a Seagate and a Western Digital disk and both exhibit the same behavior.
To remove Retrospect as a variable I wrote a simple Java program (see attachment) which opens the raw disk device and reads the entire disk 128MB at a time. This also fails within 5-10 minutes as the disk momentarily disconnects and reconnects.
I did a lot of web research and determined it was probably a USB3 power management problem, so I:
- Disabled "Allow computer to turn off this device to save power" in Device Manager for all USB hubs
- In Power Options/Advanced Settings/Hard Disk, changed "Turn off hard disk after:" to NEVER
- In Power Options/Advanced Settings/USB selective suspend, changed setting to DISABLED
None of these changed made any difference.
Then I remembered that the ASUS Z97-WS actually has a second USB3 controller, an ASMedia ASM1042 chipset, which connects to two of the six back-panel USB ports. I moved the disk docking station to one of the ASMedia ports, and all the problems disappeared. The simple Java test program runs to completion (all 2TB on the disk) and the Retrospect Media Verify operation completes successully.
Is Intel aware of this problem? Is there a fix coming? I have the current chipset drivers from Asus installed.