I don't think the bigger tier 1 enterprise vendors have really jumped on, but I've been curious to see if anyone would create a dense hotswap m.2 setup (possibly combined with traditional 3.5" HDD bays).  The only vendor I've really seen even attempt something like this is icydock:

https://www.icydock.com/goods.php?id=287


8 NVMe m.2 devices in a single 5.25" bay.  They also have another version that does 6 m.2 in 2x3.5".  You could imagine that one of the tier 1 enterprise vendors could probably do something similar on the back of a traditional 12-bay 2U 3.5" chassis.  Stick in some moderately sized high write endurance m.2 devices and you're looking at something like 2 OSD DB/WAL per NVMe.  As it is, 6:1 with 2x2.5" seems to be pretty typical and isn't terrible if you use decent drives.

Mark

On 9/9/21 12:04 PM, David Orman wrote:
Exactly, we minimize the blast radius/data destruction by allocating
more devices for DB/WAL of smaller size than less of larger size. We
encountered this same issue on an earlier iteration of our hardware
design. With rotational drives and NVMEs, we are now aiming for a 6:1
ratio based on our CRUSH rules/rotational disk sizing/nvme
sizing/server sizing/EC setup/etc.

Make sure to use write-friendly NVMEs for DB/WAL and the failures
should be much fewer and further between.

On Thu, Sep 9, 2021 at 9:11 AM Janne Johansson <icepic...@gmail.com> wrote:
Den tors 9 sep. 2021 kl 16:09 skrev Michal Strnad <michal.str...@cesnet.cz>:
  When the disk with DB died
it will cause inaccessibility of all depended OSDs (six or eight in our
environment),
How do you do it in your environment?
Have two ssds for 8 OSDs, so only half go away when one ssd dies.

--
May the most significant bit of your life be positive.
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