RBD Bench:
```
# rbd bench --io-total=1G --io-size=1M --io-type read --io-threads 1 --io-pattern seq .../vm-1004-disk-0
bench type read io_size 1048576 io_threads 1 bytes 1073741824 pattern sequential
SEC OPS OPS/SEC BYTES/SEC
1 138 144.19 151191864.43
2 355 184.64 193612603.07
3 632 218.27 228873951.46
4 838 217.13 227675080.51
elapsed: 4 ops: 1024 ops/sec: 223.97 bytes/sec: 234846661.28
```
It seems good. (234MB/s)
But if the same disk attaches to VM, poor performance.
```
# dd if=/dev/sdb of=/dev/null bs=(BLOCK_SIZE) status=progress
```
I tested increasing the block size from 512 to 4MB.
However, it is up to 22MB/s.
The same is true for Windows.
I using VirtIO SCSI.
Guest os is FreeBSD. So I can't find read_ahead_cache option.
---
With the "cache = Write through, Discard = 1" option,
On a Windows guest, I get 200MB/s or more with the command "dd ... iflag=direct bs=4194304".
In FreeBSD, it is difficult to exceed 20MB/s because increasing bs doesn't increase the speed.
```
# rbd bench --io-total=1G --io-size=1M --io-type read --io-threads 1 --io-pattern seq .../vm-1004-disk-0
bench type read io_size 1048576 io_threads 1 bytes 1073741824 pattern sequential
SEC OPS OPS/SEC BYTES/SEC
1 138 144.19 151191864.43
2 355 184.64 193612603.07
3 632 218.27 228873951.46
4 838 217.13 227675080.51
elapsed: 4 ops: 1024 ops/sec: 223.97 bytes/sec: 234846661.28
```
It seems good. (234MB/s)
But if the same disk attaches to VM, poor performance.
```
# dd if=/dev/sdb of=/dev/null bs=(BLOCK_SIZE) status=progress
```
I tested increasing the block size from 512 to 4MB.
However, it is up to 22MB/s.
The same is true for Windows.
I using VirtIO SCSI.
Guest os is FreeBSD. So I can't find read_ahead_cache option.
---
With the "cache = Write through, Discard = 1" option,
On a Windows guest, I get 200MB/s or more with the command "dd ... iflag=direct bs=4194304".
In FreeBSD, it is difficult to exceed 20MB/s because increasing bs doesn't increase the speed.
Last edited: