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

[d tbsky <tbskyd@gmail.com>]

Peter Grandi <pg@mdraid.list.sabi.co.uk>
> Also, the MDRAID write journal is usually (and should be) a lot
> smaller than a whole flash SSD unit, so you can use a small part
> of a flash SSD for write journaling and most of it for caching.

I thought journal write-back mode should use large ssd space,like
bcache which will prevent random write at all cost.
but reading the document again, it said "The flush conditions could be
free in-kernel memory cache space is low".  since the memory won't be
too large compare to normal ssd disk, maybe a small optane ssd is best
for mdadm write-journal.