Re: md disks EXTREMELY slow 12.3-STABLE

From: mike tancsa <mike_at_sentex.net>
Date: Sat, 05 Mar 2022 01:11:20 UTC 
On 3/4/2022 3:06 PM, Karl Denninger wrote:
> On 3/4/2022 14:34, infoomatic wrote:
>> On 04.03.22 17:22, Karl Denninger wrote:
>>> Load average is 0.3 yet the md0 drive is pinned at 100% busy with just
>>> 50 transactions-per-second!
>>
>> you mean md(4), the memory disk, right? ... just to be sure it is no 
>> typo
>>
> Correct.
>
> I think I've found the issue -- The "-13" build is using a vnode on 
> the spinning rust ZFS pool (albeit a fairly high-performance one 
> comprised of mirrored vdevs) for backing store.  I'm not sure WHY this 
> winds up being so insanely slow, but it does.  I'm going to move it 
> either to memory/swap (since I have a bunch) or stick it on the SSD 
> pool since creating an md in RAM is, as expected, ridiculously fast.
>

/Try doing mount -o async. It makes a big difference speed wise for writes.
/

/    ---Mike/