Re: Initdb-time block size specification

On 7/1/23 01:16, Bruce Momjian wrote:
> On Fri, Jun 30, 2023 at 04:04:57PM -0700, Andres Freund wrote:
>> Hi,
>>
>> On 2023-06-30 18:58:20 -0400, Bruce Momjian wrote:
>>>> [1] On linux I think you need to use stat() to figure out the st_dev for a
>>>> file, then look in /proc/self/mountinfo for the block device, use the name
>>>> of the file to look in /sys/block/$d/queue/physical_block_size.
>>>
>>> I just got a new server:
>>>
>>> https://momjian.us/main/blogs/blog/2023.html#June_28_2023
>>>
>>> so tested this on my new M.2 NVME storage device:
>>>
>>> $ /sys/block/nvme0n1/queue/physical_block_size
>>> 262144
>>
>> Ah, I got the relevant filename wrong. I think it's logical_block_size, not
>> physical one (that's the size of addressing). I didn't realize because the
>> devices I looked at have the same...
>
> That one reports 512 _bytes_ for me:
>
> $ cat /sys/block/nvme0n1/queue/logical_block_size
> 512
>

What does "smartctl -a /dev/nvme0n1" say? There should be something like
this:

Supported LBA Sizes (NSID 0x1)
Id Fmt Data Metadt Rel_Perf
0 - 4096 0 0
1 + 512 0 0

which says the drive supports 4k and 512B sectors, and is currently
configures to use 512B sectors.

regards

--
Tomas Vondra
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