On Thu, Jan 08, 2015 at 10:34:27AM -0500, Martin K. Petersen wrote: > As defined, the DRAT (Deterministic Read After Trim) and RZAT (Return > Zero After Trim) flags in the ATA Command Set are unreliable in the > sense that they only define what happens if the device successfully > executed the DSM TRIM command. TRIM is only advisory, however, and the > device is free to silently ignore all or parts of the request. > > In practice this renders the DRAT and RZAT flags completely useless and > because the results are unpredictable we decided to disable discard in > MD for 3.18 to avoid the risk of data corruption. > > Hardware vendors in the real world obviously need better guarantees than > what the standards bodies provide. Unfortuntely those guarantees are > encoded in product requirements documents rather than somewhere we can > key off of them programatically. So we are compelled to disabling > discard_zeroes_data for all devices unless we explicitly have data to > support whitelisting them. > > This patch whitelists SSDs from a few of the main vendors. None of the > whitelists are based on written guarantees. They are purely based on > empirical evidence collected from internal and external users that have > tested or qualified these drives in RAID deployments. > > The whitelist is only meant as a starting point and is by no means > comprehensive: > > - All intel SSD models except for 510 > - Micron M5?0/M600 > - Samsung SSDs > - Seagate SSDs > > Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx> > Reviewed-by: Christoph Hellwig <hch@xxxxxx> Applied to libata/for-3.19-fixes. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
