Re: [gentoo-user] Re: Finally got a SSD drive to put my OS on

[Mark Knecht <markknecht@gmail.com>]

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On Wed, Apr 19, 2023 at 12:39 PM Nikos Chantziaras <realnc@gmail.com> wrote:
>
> On 19/04/2023 22:26, Dale wrote:
> > So for future reference, let it format with the default?  I'm also
> > curious if when it creates the file system it will notice this and
> > adjust automatically. It might.  Maybe?
>
> AFAIK, SSDs will internally convert to 4096 in their firmware even if
> they report a physical sector size of 512 through SMART. Just a
> compatibility thing. So formatting with 4096 is fine and gets rid of the
> internal conversion.

I suspect this is right, or has been mostly right in the past.

I think technically they default to the physical block size internally
and the earlier ones, attempting to be more compatible with HDDs,
had 4K blocks. Some of the newer chips now have 16K blocks but
still support 512B Logical Block Addressing.

All of these devices are essentially small computers. They have internal
controllers, DRAM caches usually in the 1-2GB sort of range but getting
larger. The bus speeds they quote is because data is moving for the most
part in and out of cache in the drive.

In Dale's case, if he has a 4K file system block size then it's going to
send
4K to the drive and the drive will write 8 512 byte writes to put it in
flash.

If I have the same 4K file system block size I send 4K to the drive but
my physical block size is 4K so it's a single write cycle to get it
into flash.

What I *think* is true is that any time your file system block size is
smaller than the physical block size on the storage element then
simplistically you have the risk of write amplification.

What I know I'm not sure about is how inodes factor into this.

For instance:

mark@science2:~$ ls -i
35790149  000_NOT_BACKED_UP
33320794  All_Files.txt
33337840  All_Sizes_2.txt
33337952  All_Sizes.txt
33329818  All_Sorted.txt
33306743  ardour_deps_install.sh
33309917  ardour_deps_remove.sh
33557560  Arena_Chess
33423859  Astro_Data
33560973  Astronomy
33423886  Astro_science
33307443 'Backup codes - Login.gov.pdf'
33329080  basic-install.sh
33558634  bin
33561132  biosim4_functions.txt
33316157  Boot_Config.txt
33560975  Builder
33338822  CFL_88_F_Bright_Syn.xsc

If the inodes are on the disk then how are they
stored? Does a single inode occupy a physical
block? A 512 byte LBA? Something else?

I have no clue.

>
> I believe Windows always uses 4096 by default and thus it's reasonable
> to assume that most SSDs are aware of that.
>

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