Inconsistent fio results on similar VPSes on the same node

我今天在同一个节点上，在类似规格的 VPS 上运行 yabs 时，发现 fio 测试结果存在一些不一致。请参见以下三个示例。
I am seeing some inconsistency on fio tests in yabs run today on similar spec VPSes on the same node. Please see three examples below.

我不清楚发生了什么，是否与我碰巧测试的任何单个 VPS 有关，是否与其他 VPS 或某些节点进程在特定时间使用高文件 I/O 有关，或者可能是其他原因。
I'm unclear on what's happening, whether it's related to any single VPS that I happen to be testing, whether it's related to some other VPS or some node process using high file I/O at certain times, or maybe something else.

我一直在观察 iotop -b 3 -o。目前为止，没有明显的发现。
I've been watching iotop -b 3 -o a little. So far, no obvious insight.

有想法吗？谢谢！
Ideas? Thanks!

fio Disk Speed Tests (Mixed R/W 50/50) (Partition /dev/vda1):---------------------------------Block Size | 4k            (IOPS) | 64k           (IOPS)  ------   | ---            ----  | ----           ---- Read       | 193.28 MB/s  (48.3k) | 1.78 GB/s    (27.8k)Write      | 193.79 MB/s  (48.4k) | 1.79 GB/s    (28.0k)Total      | 387.07 MB/s  (96.7k) | 3.57 GB/s    (55.9k)           |                      |                     Block Size | 512k          (IOPS) | 1m            (IOPS)  ------   | ---            ----  | ----           ---- Read       | 2.12 GB/s     (4.1k) | 2.18 GB/s     (2.1k)Write      | 2.23 GB/s     (4.3k) | 2.33 GB/s     (2.2k)Total      | 4.35 GB/s     (8.5k) | 4.51 GB/s     (4.4k)
fio Disk Speed Tests (Mixed R/W 50/50) (Partition /dev/vda1):---------------------------------Block Size | 4k            (IOPS) | 64k           (IOPS)  ------   | ---            ----  | ----           ---- Read       | 193.53 MB/s  (48.3k) | 1.95 GB/s    (30.4k)Write      | 194.04 MB/s  (48.5k) | 1.96 GB/s    (30.6k)Total      | 387.57 MB/s  (96.8k) | 3.91 GB/s    (61.1k)           |                      |                     Block Size | 512k          (IOPS) | 1m            (IOPS)  ------   | ---            ----  | ----           ---- Read       | 957.00 KB/s      (1) | 18.49 MB/s      (18)Write      | 1.12 MB/s        (2) | 20.26 MB/s      (19)Total      | 2.07 MB/s        (3) | 38.75 MB/s      (37)
fio Disk Speed Tests (Mixed R/W 50/50) (Partition /dev/vda1):---------------------------------Block Size | 4k            (IOPS) | 64k           (IOPS)  ------   | ---            ----  | ----           ---- Read       | 16.51 MB/s    (4.1k) | 1.84 GB/s    (28.7k)Write      | 16.52 MB/s    (4.1k) | 1.85 GB/s    (28.9k)Total      | 33.03 MB/s    (8.2k) | 3.69 GB/s    (57.7k)           |                      |                     Block Size | 512k          (IOPS) | 1m            (IOPS)  ------   | ---            ----  | ----           ---- Read       | 2.11 GB/s     (4.1k) | 2.19 GB/s     (2.1k)Write      | 2.22 GB/s     (4.3k) | 2.34 GB/s     (2.2k)Total      | 4.34 GB/s     (8.4k) | 4.53 GB/s     (4.4k)