On 2019/11/12 1:04 下午, Michael Lyle wrote: > 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 ?). > Hi Mike, > 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. Oh, I see, thanks for your information. It seems there should be a method to permit people disable maximum writeback rate if they don't like it. -- Coly Li
