Martin Steigerwald <mar...@lichtvoll.de> wrote: >> Wear-levelling today is handled by the firmware transparently to the OS. >> Trimming only affect the filesystem's block-allocator algorithm, not >> wear-levelling. > > How should the drive know that a deleted block is a block is can use again > without the operating system telling it through trimming? > > Wear leveling the firmware of usual consumer SSDs does itself… but it can > work > better when the operating informs it of blocks which got freed by deletion. > While the firmware can know that an overwritten block is free to use again as > it always does copy on write… it has no way of knowing whether the filesystem > freed blocks by deletion of a file without the operating system telling it. > So > trimming does affect the capacity of free space the SSD can use to shuffle > blocks around.
Exactly. As an aside, I got asked to look at moving some stuff at work up to Azure. With Azure, you get billed according to the amount of used space in a virtual disk, NOT the size of the disk. I checked this by creating a large file full of zeroes and then deleting it - with the kernel I was running which didn't have TRIM support, Azure then indicated that the billable size had gone up. I didn't get round to upgrading the kernel and retrying it. _______________________________________________ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
