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Date: Sun, 04 Oct 2009 01:23:24 +0200
From: Christian Tschabuschnig <tschaboo@gmx.at>
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Subject: [dm-crypt] How will ATA-TRIM be handled?
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To: dm-crypt@saout.de

Hello,

I don't know much about the internals of filesystems or devicemapper but
I know that the kernel supports ATA-TRIM and that ext4 supports or will
soon support it.

My question is: What happens, if a dm-crypt-layer is between the
filesystem and the real block-device? Will the trim be passed through,
or will it be discarded?

Optimally, i think, both should be possible. Passing through the
information will improve performance and lifetime of a SSD and
discarding it would give less information to an attacker since the SSD
will return zeroes on LBAs that are not mapped.

Regards,
Christian