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If not supporting WRITE SAME turns out to be a security issue, it's a bug in the operating system. And yes, some filesystems do - ESX, for example, uses what t
by trasz 7y ago
If not supporting WRITE SAME turns out to be a security issue, it's a bug in the operating system.
And yes, some filesystems do - ESX, for example, uses what they call VAAI, which is a set of optional (standardized) SCSI functionality, like WRITE SAME, COMPARE AND SWAP (iirc), and server side copy.
- outworlder 7y ago> If not supporting WRITE SAME turns out to be a security issue, it's a bug in the operating system. Is it though? There is probably a big drawback in terms of resource consumption if this is not supported. Not all environments may be ok with this.
- codys 7y agoThat sounds like a performance issue, not a security issue?
- HelloNurse 7y agoThe (potential) security issue is that the operating system fails to clear disk space, possibly incorrectly assuming it has actually been cleared.
- cornishpixels 7y agoExcept that it receives an error, so if it's assuming that, it's wrong. This command is not mandated to be supported. Therefore, if an OS assumes it is supported, that's an OS problem, not the drive.
- rowanG077 7y agoI don't see how this could occur. Either you do WRITE SAME and it works or it doesn't and you have to manually issue WRITE commands.
- jjoonathan 7y agoAh, blame tennis, my favorite game! Is there an alternative non-optional strategy for achieving secure delete (or revocation semantics of some kind)? If not, this is a fundamental capability that you can't paper over by slapping an abstraction layer on top any more than you could turn a 1TB HDD into a 2TB HDD with an abstraction layer. If so, it seems to me like the bug is very much in the hard drive / standards, not in the operating system.
- kllrnohj 7y ago> Is there an alternative non-optional strategy for achieving secure delete Issue normal data writes of blocks that are filled with zeros. The same way regular data makes it to the drive just fine will also of course work for data that's all zeros.
- pixl97 7y agoWould that work on a filesystem that supports sparse files?
- throwaway373438 7y agoWe're talking about the filesystem driver itself issuing the write. The above is a discussion about whether the filesystem driver or the block device driver would issue the SCSI commands. This would never happen from userspace.
- tedunangst 7y agoWhy would you need to overwrite blocks of a sparse file? Which blocks would you be overwriting?
- jjoonathan 7y agoOh, so WRITE SAME doesn't come with "no wear leveling" semantics? That makes emulation much more reasonable.
- 7y ago