At first I had problems getting my assorted USB 3.0 drives (3 TB Seagate ST3000DM001-9YN166 with JMicron and VIA USB-SATA bridge controllers) to connect at USB 3.0 SuperSpeed. Instead, they would show up as HighSpeed (USB 2.0) devices. After disconnecting my assorted other USB 2.0 hubs and devices, that problem went away, at least.
Using 4 drives, all connected to the hub, I created a new raidz volume, and ran multiple simultaneous rsync copies to it, transferring 3 TB in total, from the Mac mini's internal SSD, internal HD, two external FireWire drives and a different USB 3.0 drive also connected to the hub. Things appeared to go well, with zpool iostat reporting write rates of between 80 and 130 MB/s and between 1.000 and 10.000 write IOPS.
However, as a test, I also connected my iPhone to the hub. It seemed to charge properly and was recognized by iTunes, but several times during the test it played the "USB connected" chime. I suspect that the USB connection was interrupted and/or the bus reset for some reason.
I also started a zpool scrub about halfway through the test. It's almost done, and shows errors:
- Code: Select all
pool: zusb
state: ONLINE
status: One or more devices has experienced an unrecoverable error. An
attempt was made to correct the error. Applications are unaffected.
action: Determine if the device needs to be replaced, and clear the errors
using 'zpool clear' or replace the device with 'zpool replace'.
scan: scrub in progress since Sun Apr 28 10:55:40 2013
3,78Ti scanned out of 3,85Ti at 41,9Mi/s, 0h26m to go
176Ki repaired, 98,38% done
config:
NAME STATE READ WRITE CKSUM
zusb ONLINE 0 0 0
raidz1-0 ONLINE 0 0 0
GPTE_EEE87000-C79D-47E7-8A38-AF4F5784EEC6 ONLINE 0 0 2 at disk7s2 (repairing)
GPTE_EA19AF8A-C371-4016-9BF1-253664AB3363 ONLINE 0 0 1 at disk8s2 (repairing)
GPTE_311D11BB-4CFE-4A7F-B734-C693E48DE7EA ONLINE 0 0 0 at disk9s2
GPTE_0C7D2F0F-A79B-464F-9F90-BB9720197974 ONLINE 0 0 1 at disk10s2 (repairing)
I don't know what caused these errors, but I draw two conclusions:
1. Current no-name USB 3.0 hard drives, connected through a GL3520 hub, running under OS X 10.8.3, are not reliable.
2. There is a very good reason ZFS checksums everything. Fear HFS+, especially over USB 3.0.