Re: [BUG] active zones exceeded error with max_open_zones

On Apr 23, 2025 / 13:11, Sean Anderson wrote:
> Hi,
> 
> I'm getting an "active zones exceeded" error when running fio with
> --rw=randwrite mode:
> 
> # fio --bs=4k --rw=randwrite --norandommap --fsync=1 --number_ios=16384 --name=flushes --direct=1 --zonemode=zbd --max_open_zones=1978 --filename=/dev/my_zone_dev
> flushes: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=psync, iodepth=1

Hi,

The block size is 4k. And according to the blkzone report, it looks like the gap
between the zone size and zone capacity is 512b. So, I guess the fio can not
fill the gap by 4k writes. It looks likely this unalignment between the gap and
the block size left unwritten small remainders in many zones, then many zones
are kept open and the device exceeded the max active zone limit. Based on this
guess, I suggest to try with 512 byte block size to align it with the gap.

> fio-3.39

Recently, I contributed a fix which handles the case many small remainders are
left by random write workload to zoned block devices [1]. The fix was upstreamed
after the fio version 3.39. I also suggest to try out the latest fio code with
4k blocksize.

[1] https://github.com/axboe/fio/commit/e2e29bf6f8300186d267fa46a7b266d14d174575