> > 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? Thanks, Niall. > > However, the idea of lop sided mirrors was discussed > a while back in the availability thread (warning, > it's long: > http://www.opensolaris.org/jive/message.jspa?messageI > =311743). There are many people who want ZFS to > support lop sided mirrors, and I've tried to raise an > RFE twice, but I don't believe I've ever seen a bug > ID for it, it seems to get lost in the system. > > And yes, the resilver estimates are all over the > place, even when you don't allow for the fact that it > still restarts regularly. Would you be able to get > away with just reporting the percentage complete and > ignoring the estimates until that code is improved? > > Ross -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
