On 06/12/2024 23:31, Michael Stone wrote:
On Fri, Dec 06, 2024 at 10:51:20PM +0700, Max Nikulin wrote:
Michael, thank you for the long message. Actually I wonder what is
"idle" that allows drive to perform self-maintenance. I expect that
the device should not be in some deep power saving state (I am yet to
discover available tunables that allows drive to "sleep"). Should it
be some period of time (seconds? minutes?) completely without any IO
or is it enough if read/write speed is below some threshold and from/
to another chip?
Basically it means that it isn't busy doing I/O; if you're reading or
writing, the drive can't also be reading and writing. It doesn't need to
be absolutely unused.
Accidentally I noticed a link suggesting that USB enclosure may be more
effective than booting to system firmware menu. I am curious if it is
just an invention of support staff or it is blessed by SSD firmware
developers:
<https://www.crucial.com/support/articles-faq-ssd/why-did-ssd-disappear-from-system>
"Why Did my SSD 'Disappear' from my System?"
My experience is that at least USB enclosures for HDD may be quite
aggressive in respect to power saving. It is linked from
<https://www.truenas.com/community/threads/killed-an-nvme-drive-running-a-long-smart-test.114125/>
"Killed an NVMe drive running a long SMART test" Nov 11, 2023
As to erase block size, I am aware of it. On the other hand I am
surprised that a drive does not allow kernel to optimize writes on a
higher level (as uSD does):
grep '' /sys/block/*/queue/discard_granularity
...
/sys/block/mmcblk0/queue/discard_granularity:4194304
/sys/block/nvme0n1/queue/discard_granularity:4096
/sys/block/sda/queue/discard_granularity:4096 # hdd (shingled)
I do not think it is relevant, but sorry for the confusion concerning
"shingled", it is not. This disk has another issue: short heads
unloading timeout that is not configurable using hdparm.
The discard_granularity *limits* how the kernel can tell the drive that
there are free blocks--a granularity of 4M means that the kernel can
only issue a TRIM command when it has at least 4M of empty space *and*
that empty space is aligned on a 4M boundary. (That is, you can't
discard locations 2-5M on the drive, only 0-3M, 4-7M, etc.) It's a big
number on the sd card because sd cards are pretty much junk. On a decent
NVMe drive it'll typically be 512 (i.e., you can discard any logical
block) or maybe 4096 if you're in 4k mode.
I switched this NVME drive to 4k mode. However I considered your message
as statement that internally drives still use higher erase block size
<https://lists.debian.org/msgid-search/cc8f9e0a-b31f-11ef-9b6a-00163eeb5...@msgid.mathom.us>
Thu, 5 Dec 2024 12:41:55 -0500
