I have an odd setup at present, because I'm testing while still building my machine.
It's an Intel Atom D510 mobo running snv_134 2GB RAM with 2 SATA drives (AHCI): 1: Samsung 250GB old laptop drive 2: WD Green 1.5TB drive (idle3 turned off) Ultimately, it will be a time machine backup for my Mac laptop. So I have installed Netatalk 2.1.1 which is working great. Read performance from the mirror, via gigabit ethernet rocks, easily sustaining 50MB/s off the two drives mirrored. However, write performance is terrible, typically no better than 1-2MB/s on average. I just thought to detach the WD drive from the mirror and test the drives individually, so with the system still running on drive 1 I create an independent zpool on the other drive and a netatalk share to it. Using `dd` to copy a single large file, to each drive the results are: Drive 1: Samsung (rpool, and there's a scrub going on) 1565437216 bytes transferred in 98.236700 secs (15935360 bytes/sec) Drive 2: Western Digital 1.5TB green drive: 1565437216 bytes transferred in 71.745737 secs (21819237 bytes/sec) However, when the two drives were mirrored, after all resilvering completed and there was no background I/O, the write performance was about 10x worse. Watching `zpool iostat -v 2` I could see that quite often drive 1 would write a big chunk of data and then wait for ages for drive 2 to write the same data to disc. Could it be that there is a separate cache for the mirror that was stalling waiting on the cache for the larger drive?? Would this scenario be caused because the drives are so different in size? 250GB and 1500GB?? Once the scrub finishes, I'll re-attach the mirror, and re-test tomorrow, reporting the `zpool iostat` in detail... -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
