I run two 1.5TB Optanes in raid-0 with XFS (I picked them up for $300 each on sale about two years ago). These are limited to PCIE 3.0 x4 (about 4GB/s max each). I also have a 64GB optane drive I use as my boot drive.

It's hard to tell you, because it's subjective, I don't swap back and forth between an SSD and the optane drives. I have my old system, which has a 2TB Samsung 980 Pro NVME drive (PCIE 4.0 x4, or 8GB/s max) as root, and a Sabrent rocket 4 plus 4TB drive secondary (also PCIE 4.0), so I ran sysbench on both systems, so I could share the differences. (Old system 5950X, new system 9950X3D).

It feels snappier, especially when doing compilations...

Sequential reads: I started with a 150GB fileset, but it was being served by the kernel cache on my newer system (256GB RAM vs 128GB on the old), so I switched to use 300GB of data, and the optanes gave me 5000 MiB/s for sequential read as opposed to 2800 MiB/s for the 980 Pro, and 4340 MiB/s for the Rocket 4 Plus.

Random writes alone (no read workload) The optane system gets 2184 MiB/s, the 980 Pro gets 32 MiB/s, and the Rocket 4 Plus gets 53 MiB/s.

Mixed workload (random read/write) The optanes get 725/483 as opposed to 9/6 for the 980 Pro, and 42/28 for the Rocket 4 Plus.

2x1.5TB Optane Raid0: Prep time: `sysbench fileio --file-total-size=150G prepare` 161061273600 bytes written in 50.41 seconds (3047.27 MiB/sec).

    Benchmark:
    `sysbench fileio --file-total-size=150G --file-test-mode=rndrw --max-time=60 --max-requests=0 run`
    WARNING: --max-time is deprecated, use --time instead
    sysbench 1.0.20 (using system LuaJIT 2.1.1741730670)

    Running the test with following options:
    Number of threads: 1
    Initializing random number generator from current time

    Extra file open flags: (none)
    128 files, 1.1719GiB each
    150GiB total file size
    Block size 16KiB
    Number of IO requests: 0
    Read/Write ratio for combined random IO test: 1.50
    Periodic FSYNC enabled, calling fsync() each 100 requests.
    Calling fsync() at the end of test, Enabled.
    Using synchronous I/O mode
    Doing random r/w test
    Initializing worker threads...

    Threads started!

    File operations:
        reads/s:                      46421.95
        writes/s:                     30947.96
        fsyncs/s:                     99034.84

    Throughput:
        read, MiB/s:                  725.34
        written, MiB/s:               483.56

    General statistics:
        total time:                          60.0005s
        total number of events:              10584397

    Latency (ms):
             min:                                    0.00
             avg:                                    0.01
             max:                                    1.32
             95th percentile:                        0.03
             sum:                                58687.09

    Threads fairness:
        events (avg/stddev):           10584397.0000/0.00
        execution time (avg/stddev):   58.6871/0.00

    Benchmark:
    `sysbench fileio --file-total-size=150G --file-test-mode=rndrw --max-time=60 --max-requests=0 run`
    WARNING: --max-time is deprecated, use --time instead
    sysbench 1.0.20 (using system LuaJIT 2.1.1741730670)

    Running the test with following options:
    Number of threads: 1
    Initializing random number generator from current time

    Extra file open flags: (none)
    128 files, 1.1719GiB each
    150GiB total file size
    Block size 16KiB
    Number of IO requests: 0
    Read/Write ratio for combined random IO test: 1.50
    Periodic FSYNC enabled, calling fsync() each 100 requests.
    Calling fsync() at the end of test, Enabled.
    Using synchronous I/O mode
    Doing random r/w test
    Initializing worker threads...

    Threads started!

    File operations:
        reads/s:                      594.34
        writes/s:                     396.23
        fsyncs/s:                     1268.87

    Throughput:
        read, MiB/s:                  9.29
        written, MiB/s:               6.19

    General statistics:
        total time:                          60.0662s
        total number of events:              135589

    Latency (ms):
             min:                                    0.00
             avg:                                    0.44
             max:                                   15.35
             95th percentile:                        1.73
             sum:                                59972.76

    Threads fairness:
        events (avg/stddev):           135589.0000/0.00
        execution time (avg/stddev):   59.9728/0.00

    Benchmark:
    `sysbench fileio --file-total-size=300G --file-test-mode=rndrw --max-time=60 --max-requests=0 run`
    WARNING: --max-time is deprecated, use --time instead
    sysbench 1.0.20 (using system LuaJIT 2.1.1741730670)

    Running the test with following options:
    Number of threads: 1
    Initializing random number generator from current time

    Extra file open flags: (none)
    128 files, 2.3438GiB each
    300GiB total file size
    Block size 16KiB
    Number of IO requests: 0
    Read/Write ratio for combined random IO test: 1.50
    Periodic FSYNC enabled, calling fsync() each 100 requests.
    Calling fsync() at the end of test, Enabled.
    Using synchronous I/O mode
    Doing random r/w test
    Initializing worker threads...

    Threads started!

    File operations:
        reads/s:                      2690.28
        writes/s:                     1793.52
        fsyncs/s:                     5740.92

    Throughput:
        read, MiB/s:                  42.04
        written, MiB/s:               28.02

    General statistics:
        total time:                          60.0155s
        total number of events:              613520

    Latency (ms):
             min:                                    0.00
             avg:                                    0.10
             max:                                    8.22
             95th percentile:                        0.32
             sum:                                59887.69

    Threads fairness:
        events (avg/stddev):           613520.0000/0.00
        execution time (avg/stddev):   59.8877/0.00