First test is using iozone against the mounted nbd device
The nbd device is a 4GB disk with 1GB cache only.
the test writes/read/and rewrite a 1GB file, which means we live at the age of cache file. So rewrite,
and random writes will definitely cause a cache evictions and loading from backend. The cache is also full (no free spce in cache) is entirely allocated
by pages.
Note since i am running this on my laptop, where i don't have HDD the backend also live on an SSD device
the test command as shown in the output below is iozone -t1 -i0 -i2 -r1k -s1g /mnt/nbd
Run began: Tue Nov 14 13:13:25 2023
Record Size 1 kB
File size set to 1048576 kB
Command line used: iozone -t1 -i0 -i2 -r1k -s1g /mnt/nbd
Output is in kBytes/sec
Time Resolution = 0.000001 seconds.
Processor cache size set to 1024 kBytes.
Processor cache line size set to 32 bytes.
File stride size set to 17 * record size.
Throughput test with 1 process
Each process writes a 1048576 kByte file in 1 kByte records
Children see throughput for 1 initial writers = 421528.94 kB/sec
Parent sees throughput for 1 initial writers = 237488.97 kB/sec
Min throughput per process = 421528.94 kB/sec
Max throughput per process = 421528.94 kB/sec
Avg throughput per process = 421528.94 kB/sec
Min xfer = 1048576.00 kB
Children see throughput for 1 rewriters = 388271.31 kB/sec
Parent sees throughput for 1 rewriters = 229103.80 kB/sec
Min throughput per process = 388271.31 kB/sec
Max throughput per process = 388271.31 kB/sec
Avg throughput per process = 388271.31 kB/sec
Min xfer = 1048576.00 kB
Children see throughput for 1 random readers = 673925.38 kB/sec
Parent sees throughput for 1 random readers = 653746.85 kB/sec
Min throughput per process = 673925.38 kB/sec
Max throughput per process = 673925.38 kB/sec
Avg throughput per process = 673925.38 kB/sec
Min xfer = 1048576.00 kB
Children see throughput for 1 random writers = 13213.84 kB/sec
Parent sees throughput for 1 random writers = 13139.41 kB/sec
Min throughput per process = 13213.84 kB/sec
Max throughput per process = 13213.84 kB/sec
Avg throughput per process = 13213.84 kB/sec
Min xfer = 1048576.00 kB
iozone test complete.
This test runs against my ssd directly as shown in the command line used
Run began: Tue Nov 14 13:16:17 2023
Record Size 1 kB
File size set to 1048576 kB
Command line used: iozone -t1 -i0 -i2 -r1k -s1g /opt
Output is in kBytes/sec
Time Resolution = 0.000001 seconds.
Processor cache size set to 1024 kBytes.
Processor cache line size set to 32 bytes.
File stride size set to 17 * record size.
Throughput test with 1 process
Each process writes a 1048576 kByte file in 1 kByte records
Children see throughput for 1 initial writers = 403285.28 kB/sec
Parent sees throughput for 1 initial writers = 236887.53 kB/sec
Min throughput per process = 403285.28 kB/sec
Max throughput per process = 403285.28 kB/sec
Avg throughput per process = 403285.28 kB/sec
Min xfer = 1048576.00 kB
Children see throughput for 1 rewriters = 497541.16 kB/sec
Parent sees throughput for 1 rewriters = 256352.72 kB/sec
Min throughput per process = 497541.16 kB/sec
Max throughput per process = 497541.16 kB/sec
Avg throughput per process = 497541.16 kB/sec
Min xfer = 1048576.00 kB
Children see throughput for 1 random readers = 619068.94 kB/sec
Parent sees throughput for 1 random readers = 602831.53 kB/sec
Min throughput per process = 619068.94 kB/sec
Max throughput per process = 619068.94 kB/sec
Avg throughput per process = 619068.94 kB/sec
Min xfer = 1048576.00 kB
Children see throughput for 1 random writers = 27818.76 kB/sec
Parent sees throughput for 1 random writers = 26177.42 kB/sec
Min throughput per process = 27818.76 kB/sec
Max throughput per process = 27818.76 kB/sec
Avg throughput per process = 27818.76 kB/sec
Min xfer = 1048576.00 kB
iozone test complete.