there is this thing called NVM which people have been using for write cache for the better part of a decade now, maybe you should consider using one of those instead… also then you could do sync writes as well because it’s on disk, ofc that depends on what your cache software will allow you to do…
i’m very happy with my mediocre at best MLC write cache on to which i force both async and sync writes to so that i get more sequential writes onto the HDD, instead of async and sync unloading on their own cycles… thus i basically half my write IO / write time to the HDD / accesses.
this inturn improves my read latency, because the disks can more easily keep up.
if one can say anything is easy about keeping up with the Storagenode IO
ofc this isn’t the perfect solution for everything… but imo it seems to work better than what else i’ve tried.