Per commit ac8fa4196d20: > md: allow resync to go faster when there is competing IO. > > When md notices non-sync IO happening while it is trying to resync (or > reshape or recover) it slows down to the set minimum. > > The default minimum might have made sense many years ago but the drives have > become faster. Changing the default to match the times isn't really a long > term solution. This holds true for modern hardware, but this commit is causing problems on older hardware, like SGI MIPS platforms, that use mdraid. Namely, while trying to chase down an unrelated hardlock bug on an Onyx2, one of the arrays got out of sync, so on the next reboot, mdraid's attempt to resync at full speed absolutely murdered interactivity. It took close to 30mins for the system to finally reach the login prompt. Revert this patch was working to mitigate the problem at first, but it appears that in recent kernels, this is no longer the case, and reverting this commit has no noticeable effect anymore. I assume I'd have to hunt down newer commits to revert, but it's probably saner to just highlight the problem and test any proposed solutions. Is there some way to resolve this in such a way that old hardware maintains some level of interactivity during a resync, but that won't inconvenience the more modern systems? http://git.linux-mips.org/cgit/ralf/linux.git/commit/?id=ac8fa4196d20 Thanks!, --J -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
