>>>>> "Cláudio" == Cláudio Martins <ctpm@xxxxxxxxxx> writes: Cláudio> So the question is: what are hard drive makers guaranteeing (if Cláudio> anything at all)? No guarantees. Nothing that you can get in writing, anyway. Cláudio> Was a 512B sector write really atomic? Sometimes. Cláudio> Is a 4k one? Sometimes, maybe. The problem with 4KB physical blocks is that if you do a partial or misaligned write you'll end up having to do read-modify-write. And that introduces are scenario where a subsequent write error will affect logical blocks that were not part of the I/O request. However, you also have that with regular drives because they often write more than the actual block undergoing I/O. For instance to reduce hotspot bleed to adjacent sectors. There have been several unsuccessful attempts at nudging the drive vendors into giving us real guarantees (supercapacitors, NVRAM or flash-backed write cache). No luck so far. So people that care use arrays with non-volatile caches. -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
