Everything I Know About SSDs
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Everything I Know About SSDs
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Re: Everything I Know About SSDs
#2The part about filesystems is slightly incorrect.
> The way the file system handles this is incompatible with the workings of NAND flash.
That's true of most conventional filesystems, but log-structured filesystems are much more flash-friendly. That's why there has been a resurgence of interest in them, and also why a typical flash translation layer bears a striking resemblance to a log-structured FS. There are also flash-specific filesystems.
> to an HDD all sectors are the same.
This is not true because of bad blocks. Every disk has a reserve of blocks that can be remapped in place of a detected bad block, transparently, much like flash blocks are remapped. Beyond that, it's also useful for a disk to know which blocks are not in use so it can return all zeroes without actually hitting the media. There are special flags to force media access and commands to physically zero a block, for the cases where those are needed, but often they're not. Trim/discard actually gets pretty complicated, especially when things like RAID and virtual block devices are involved.
Re: Everything I Know About SSDs
#3I was under the impression that if you do not encrypt an SSD from the first use, then any attempt at overwriting with 0s is futile, as well as any other method to securely delete the files. The files will be easily recovered.
This guy seems to say the opposite, in that the files are "simply not there anymore", contrary to everything I've read: who's right here?
Re: Everything I Know About SSDs
#4I was under the impression that if you do not encrypt an SSD from the first use, then any attempt at overwriting with 0s is futile, as well as any other method to securely delete the files. The files will be easily recovered. This guy seems to say the opposite, in that the files are "simply not there anymore", contrary to everything I've read: who's right here?
In practice all SSDs are always encrypted because they use the encryption to whiten the data written to them. That's why "Secure Erase" takes less than a second on SSDs, it doesn't erase anything but the key.
Re: Everything I Know About SSDs
#5I was under the impression that if you do not encrypt an SSD from the first use, then any attempt at overwriting with 0s is futile, as well as any other method to securely delete the files. The files will be easily recovered. This guy seems to say the opposite, in that the files are "simply not there anymore", contrary to everything I've read: who's right here?
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Re: Everything I Know About SSDs
#6There's some interesting content about SSDs and HDDs here:
SSDs: https://superuser.com/questions/tagged/ssd?tab=Votes
HDDs: https://superuser.com/questions/tagged/hard-drive?tab=Votes
Re: Everything I Know About SSDs
#7I was under the impression that if you do not encrypt an SSD from the first use, then any attempt at overwriting with 0s is futile, as well as any other method to securely delete the files. The files will be easily recovered. This guy seems to say the opposite, in that the files are "simply not there anymore", contrary to everything I've read: who's right here?
In practice all SSDs are always encrypted because they use the encryption to whiten the data written to them. That's why "Secure Erase" takes less than a second on SSDs, it doesn't erase anything but the key.
But AFAIK this isn't true for all solid state storage, like cheap USB memory keys. These would generally also benefit from log structured filesystems - but really should be encrypted too.
(which is one great promise of zfs on linux/openzfs - cross-platform encrypted removable storage).
Re: Everything I Know About SSDs
#8There are a few technologies that I’ve tried very earnestly to understand, only to find out that it’s basically black magic and there’s no use in trying to understand it. Those things are modern car transmissions, nuclear reactors, and SSDs.
Re: Everything I Know About SSDs
#9I was under the impression that if you do not encrypt an SSD from the first use, then any attempt at overwriting with 0s is futile, as well as any other method to securely delete the files. The files will be easily recovered. This guy seems to say the opposite, in that the files are "simply not there anymore", contrary to everything I've read: who's right here?
In practice all SSDs are always encrypted because they use the encryption to whiten the data written to them. That's why "Secure Erase" takes less than a second on SSDs, it doesn't erase anything but the key.
Interesting! Do you happen to know which encryption algorithm is used? I would think that, if the only goal is whitening (as opposed to robust security), a fairly weak algorithm would be used, or perhaps a strong algorithm with a reduced number of rounds.
Re: Everything I Know About SSDs
#10I was under the impression that if you do not encrypt an SSD from the first use, then any attempt at overwriting with 0s is futile, as well as any other method to securely delete the files. The files will be easily recovered. This guy seems to say the opposite, in that the files are "simply not there anymore", contrary to everything I've read: who's right here?
> The files will be easily recovered.
Not really “easily”. At the very least you’ll need a modded flash controller that can bypass the flash translation layer. Also, on SSDs with TRIM support you’re also racing against the garbage collector which will erase any unused (ie. deleted) blocks.