Niall Power wrote: >> Yes to both I believe, while the USB device is >> attached your system will run slower, and it will run >> considerably slower while replicating data. >> Hopefully USB 3 or eSATA drives would address this >> to some extent. > > I think I've confirmed this is the case, at least in the configuration > I tried. With a USB mirror device configured a time write of a 200m > file took about 19 seconds on average with the USB drive detached. > After reattaching and waiting for the resilver to complete, the write took > on average 25 seconds. Detaching the USB mirror from the pool entirely > and just having the single laptop disk in the pool gave the best results > at about 16 seconds average. Obviously this is all purely anecdotal data > but it would appear to agree with the presumptions. > On a positive note, it seems that the performance hit is much worse for > when both sides of the mirror are online, compared to when it's detached > and the pool is degraded but I'm sure that we'll pay for it later when the > disk is reattached later and it resilvers. But maybe that's acceptable for > our target audience. > It definitely seems like there are performance issues that I need to better > understand before jumping in feet first with this. > Would a lop sided mirror behave any differently in comparison to this? > Does it also ensure that writes are sent to all sides of the mirror before > returning?
Different USB memory sticks vary enormously in speed. The speed is often not described on the packaging, so it's often not possible to know how fast one is until after you've bought it and tried it. -- Andrew _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
