>>>>> "Phillip" == Phillip Susi <psusi@xxxxxxxxxx> writes: >> We have means of obtaining alignment and physical sector size >> information from both SCSI and ATA drives. But only if the drive >> firmware provides the information, of course. Phillip> How? http://oss.oracle.com/~mkp/docs/linux-advanced-storage.pdf Phillip> I don't see any such information in the output of hdparm -I for Phillip> instance. You need hdparm-9.27 or later. >> One currently shipping drive model on the market isn't reporting the >> bigger physical block size. But there are several other 4KB sector >> products out there that are working just fine. Phillip> The WD drive indeed reports a 512 byte sector size, but I also Phillip> have an SSD with a 512kb erase block size and it seems like Phillip> these knobs were intended to cover that as well, but again, the Phillip> values exported by the kernel in /sys are 0 and I don't see a Phillip> way for the drive to report this information to the kernel. There are no means to report things like the erase block size. A few years ago there was a push in the industry to define a set of parameters that would make sense for flash drives. For a variety of reasons, however, this effort never really took off. There are some things in the pipeline but it's mostly statistics and life expectancy stuff. On well-designed drives the erase block size and other physical characteristics do not matter because the firmware uses an approach akin to a log-structured filesystem. For low-end devices (where we could potentially benefit from knowing the physical characteristics) the problem is that this information is often considered part of the vendor's secret sauce. Another common concern is that exporting a set of metrics squarely puts the drive in the "poorly designed" bucket and that's a marketing disaster. It is a lengthy process to get stuff pushed through the standards organizations. Even if the industry had been successful in defining a set of SSD characteristics it would have taken quite a while for things to get ratified and show up in devices. The expectation was that early SSD designs exhibiting side effects from being flash-based would be obsolete by then. And as it turns out you can get an SSD with a sane firmware for $100 and change these days... -- Martin K. Petersen Oracle Linux Engineering -- 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
