On Mon, Nov 11, 2019 at 9:00 PM Coly Li <colyli@xxxxxxx> wrote: > It seems Areca RAID adapter can not handle high random I/O pressure > properly and even worse then regular write I/O rate (am I right ?). I believe what his data shows is that when the only workload is writeback, it's all random write and isn't coalesced. Areca is pretty good with random write, but because we sort on LBA already the adapter cache provides no benefit to allow further I/O coalescing. OTOH, I liked the system we had before where we had at most 1 idle writeback outstanding at a time, because it was guaranteed to not create excessive load on the cache or backing device. I think his chief objection is that he uses the cache device for other things and doesn't want its idle utilization to be high. Mike
