> LVM like md raid and drbd is a layered block device and > If you turn the wire caches off on the HDs then there is no problem, > but HDs aren't designed to perform to spec with the write cache > disabled they expect important data is written with FUA access (forced > unit access), so performance will be terrible. I hope that I'm not going too much off topic here, but I'm getting worried not to be sure to understand, especially when it has to do with data safety: Considering a stack of: - ext3 - on top of LVM2 - on top of software RAID1 - on top of regular SATA disks (no hardware RAID) is it "safe" to have the HD cache enabled? (Note: ext3, not XFS, hence the possible off-topic...) In other words, is this discussion about barriers, etc. only relevant to XFS?