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Re: Beating a dead horse

On Wed, 25 Nov 2015, Andreas Gustafsson wrote:
The don't have sectors as much as flash pages, and the page size varies from device to device.

I'm curious about something, probably due to ignorance of the full dynamics of the vfs(9) layer. Why is it that folks don't choose file system block sizes and partition offsets that are least-common-factors that they share with the hardware layer. Ie.. Let's say the hard disk uses 4K pages, the file system uses 8K blocks, and the vendor recommends that you stay aligned with a 1GB value. Wouldn't operating on 8K blocks still satisfy the underlying device (since 8K operations would always be divisible by a factor of 4K) and the 1GB alignment may not always be perfect, but the 8K ops below it would eventually stack to 1GB exactly, too.

Is it all about waste at the file system layer due to some block operations being optimized for large devices and buffers but not being as applicable (or being downright wasteful) on smaller block devices?

I'm just asking so I can better follow the conversation you more experienced folks are having.


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