Re: use ssd as write-journal or lvm-cache?

quoted

[...] ps: my ssd is intel dc grade, so I think enable
write-back mode of cache is not problem. [...]

Not all "enterprise" grade flash SSD models have persistent
buffers though, so better check.

In any case, in order to not add a single point of failure to
the array, better rely not on SSD being a "datacenter" one
(anything can fail), but use a RAID1 of two SSDs.

The main point of "enterprise" flash SSD models is (as the
original poster wrote) the ability to enable write-back (thus
much, much higher committed write rates), if they have
persistent buffering. Higher "endurance" and reliability are
secondary points. With redundant units having models with
persistent buffering is even more important too.