David Lethe wrote: > Fyi - related problem is seen with solaris & zfs when users attach them > to hardware-based RAID subsystems. The vendors had > to make firmware tweaks to address solaris's > flush-to-disk-after-all-writes. > > Not sure what you mean about non-volatile vs. volatile write cache, > however. If you want to see if write cache is enabled on a disk drive, > or > Even a logical disk on a hardware-based RAId, under Linux, then google > "mode page editor" for lots of choices. Also look up zfs write cache > raid and you'll get information that you can just as easily apply to > Linux implementations of md. I'm not so interested in whether it is enabled; I'd like to know if it is safe (to varying degrees) in the event of a power failure, and I don't think there's any way we can know that. So the administrator, if she's sure that all cached writes will hit disk even if a breaker pops, can disable barriers. If it's just a 32MB cache seagate drive plugged into the wall, you probably had better be sure barriers are enabled or you may well have a scrambled filesystem post-power-outage. -Eric -- 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
