Just happened again. Any thoughts about where I should start looking? Mon Apr 15 11:01:40 EDT 2019 4k100test: (g=0): rw=randread, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=libaio, iodepth=1024 ... fio-3.1 Starting 12 processes 4k100test: Laying out IO file (1 file / 1024MiB) fio: native_fallocate call failed: Operation not supported 4k100test: Laying out IO file (1 file / 1024MiB) fio: native_fallocate call failed: Operation not supported 4k100test: Laying out IO file (1 file / 1024MiB) fio: native_fallocate call failed: Operation not supported 4k100test: Laying out IO file (1 file / 1024MiB) fio: native_fallocate call failed: Operation not supported 4k100test: Laying out IO file (1 file / 1024MiB) fio: native_fallocate call failed: Operation not supported 4k100test: Laying out IO file (1 file / 1024MiB) fio: native_fallocate call failed: Operation not supported 4k100test: Laying out IO file (1 file / 1024MiB) fio: native_fallocate call failed: Operation not supported 4k100test: Laying out IO file (1 file / 1024MiB) fio: native_fallocate call failed: Operation not supported 4k100test: Laying out IO file (1 file / 1024MiB) fio: native_fallocate call failed: Operation not supported 4k100test: Laying out IO file (1 file / 1024MiB) fio: native_fallocate call failed: Operation not supported 4k100test: Laying out IO file (1 file / 1024MiB) fio: native_fallocate call failed: Operation not supported 4k100test: Laying out IO file (1 file / 1024MiB) fio: native_fallocate call failed: Operation not supported fio: io_u error on file 4k100test.7.0: Invalid slot: read offset=938229760, buflen=4096 fio: pid=2653, err=57/file:io_u.c:1756, func=io_u error, error=Invalid slot fio: io_u error on file 4k100test.10.0: Invalid slot: read offset=331800576, buflen=40963s] fio: pid=2650, err=57/file:io_u.c:1756, func=io_u error, error=Invalid slot Jobs: 10 (f=10): [r(2),X(1),r(2),X(1),r(6)][100.0%][r=617MiB/s,w=0KiB/s][r=158k,w=0 IOPS][eta 00m:00s] 4k100test: (groupid=0, jobs=12): err=57 (file:io_u.c:1756, func=io_u error, error=Invalid slot): pid=2648: Mon Apr 15 11:02:25 2019 read: IOPS=157k, BW=613MiB/s (643MB/s)(11.4GiB/19024msec) slat (usec): min=2, max=9808, avg= 7.36, stdev=30.80 clat (usec): min=43, max=1236.1k, avg=74443.93, stdev=85310.03 lat (usec): min=134, max=1236.1k, avg=74451.53, stdev=85309.77 clat percentiles (usec): | 1.00th=[ 807], 5.00th=[ 1287], 10.00th=[ 1647], 20.00th=[ 2376], | 30.00th=[ 3490], 40.00th=[ 8160], 50.00th=[ 69731], 60.00th=[ 76022], | 70.00th=[ 80217], 80.00th=[139461], 90.00th=[181404], 95.00th=[233833], | 99.00th=[375391], 99.50th=[438305], 99.90th=[549454], 99.95th=[616563], | 99.99th=[750781] bw ( KiB/s): min=46941, max=70036, per=8.73%, avg=54819.99, stdev=4131.49, samples=430 iops : min=11735, max=17509, avg=13704.80, stdev=1032.88, samples=430 lat (usec) : 50=0.01%, 100=0.01%, 250=0.01%, 500=0.14%, 750=0.63% lat (usec) : 1000=1.48% lat (msec) : 2=12.84%, 4=17.70%, 10=7.87%, 20=0.77%, 50=0.21% lat (msec) : 100=34.04%, 250=20.30%, 500=3.82%, 750=0.20%, 1000=0.01% lat (msec) : 2000=0.01% cpu : usr=2.04%, sys=7.06%, ctx=698855, majf=0, minf=6299 IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=0.1%, 32=0.1%, >=64=100.0% submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0% complete : 0=0.1%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.1% issued rwt: total=2986716,0,0, short=0,0,0, dropped=0,0,0 latency : target=0, window=0, percentile=100.00%, depth=1024 Run status group 0 (all jobs): READ: bw=613MiB/s (643MB/s), 613MiB/s-613MiB/s (643MB/s-643MB/s), io=11.4GiB (12.2GB), run=19024-19024msec -- Chuck Lever