root@odroid:~# zpool status
  pool: cottage
 state: ONLINE
status: Some supported features are not enabled on the pool. The pool can
        still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
        the pool may no longer be accessible by software that does not support
        the features. See zpool-features(5) for details.
  scan: scrub in progress since Fri Aug  3 12:18:24 2018
        7.39T scanned at 181M/s, 7.25T issued at 177M/s, 31.7T total
        0B repaired, 22.88% done, 1 days 16:08:51 to go
config:

        NAME        STATE     READ WRITE CKSUM
        cottage     ONLINE       0     0     0
          raidz1-0  ONLINE       0     0     0
            sda     ONLINE       0     0     0
            sdf     ONLINE       0     0     0
            sdc     ONLINE       0     0     0
            sde     ONLINE       0     0     0
            sdd     ONLINE       0     0     0
            sdb     ONLINE       0     0     0

errors: No known data errors
root@odroid:~# [167418.086141] INFO: rcu_preempt detected stalls on CPUs/tasks:
[167418.090444]         4-...: (0 ticks this GP) idle=65e/140000000000000/0 softirq=30601400/30601401 fqs=2306
[167418.099612]         5-...: (0 ticks this GP) idle=346/140000000000000/0 softirq=29833347/29833347 fqs=2306
[167418.108795]         6-...: (0 ticks this GP) idle=7c2/140000000000000/0 softirq=30575104/30575104 fqs=2306
[167418.117981]         7-...: (1 GPs behind) idle=04e/140000000000000/0 softirq=30454365/30454367 fqs=2306
[167418.126904]         (detected by 1, t=5252 jiffies, g=13128296, c=13128295, q=260)
[167481.104070] INFO: rcu_preempt detected stalls on CPUs/tasks:
[167481.108381]         4-...: (0 ticks this GP) idle=65e/140000000000000/0 softirq=30601400/30601401 fqs=4831
[167481.117548]         5-...: (0 ticks this GP) idle=346/140000000000000/0 softirq=29833347/29833347 fqs=4832
[167481.126733]         6-...: (0 ticks this GP) idle=7c2/140000000000000/0 softirq=30575104/30575104 fqs=4832
[167481.135918]         7-...: (1 GPs behind) idle=04e/140000000000000/0 softirq=30454365/30454367 fqs=4832
[167481.144839]         (detected by 2, t=21017 jiffies, g=13128296, c=13128295, q=1033)
[167521.185106] rcu_preempt kthread starved for 10008 jiffies! g13128296 c13128295 f0x0 RCU_GP_DOING_FQS(4) ->state=0x0 ->cpu=0