带有随机读/写的SSD原始I/O基准

我的笔记本电脑有一个SSD磁盘，物理磁盘扇区大小为512字节，逻辑磁盘扇区大小为4,096字节。我正在研究一个ACID数据库系统，其中有绕过所有操作系统缓存，因此我直接从分配的内部内存(RAM)写入SSD磁盘。我还在运行测试之前扩展文件，并且在测试期间不调整其大小。

现在这是我的问题，根据SSD基准随机读取&写速率应该分别在30 MB/s到90 MB/s之间。但以下是我从众多性能测试中获得的遥测结果(相当糟糕):

• 读取随机512字节块(物理扇区大小)时1.2 MB/s
• 写入随机512字节块(物理扇区大小)时512 KB/s
• 8.5 MB/s读取随机4,096字节块(逻辑扇区大小)
• 当写入随机4,096字节块(逻辑扇区大小)时4.9 MB/s

除了使用异步I/O之外，我还设置了FILE_SHARE_READ和FILE_SHARE_WRITE标志来禁用所有操作系统缓冲-因为我们的数据库是ACID，我必须这样做，我还尝试了FlushFileBuffers()，但这给了我更差的性能。我还等待每个异步I/O操作完成，这是我们的一些代码所要求的。

这是我的代码，是有问题，还是我坚持这个糟糕的I/O性能?

HANDLE OpenFile(const wchar_t *fileName)
{
    // Set access method
    DWORD desiredAccess = GENERIC_READ | GENERIC_WRITE ;
    // Set file flags
    DWORD fileFlags = FILE_FLAG_WRITE_THROUGH | FILE_FLAG_NO_BUFFERING /*| FILE_FLAG_RANDOM_ACCESS*/;
    //File or device is being opened or created for asynchronous I/O
    fileFlags |= FILE_FLAG_OVERLAPPED ;
    // Exlusive use (no share mode)
    DWORD shareMode = 0;
    HANDLE hOutputFile = CreateFile(
        // File name
        fileName,
        // Requested access to the file 
        desiredAccess,
        // Share mode. 0 equals exclusive lock by the process
        shareMode,
        // Pointer to a security attribute structure
        NULL,
        // Action to take on file
        CREATE_NEW,
        // File attributes and flags
        fileFlags,
        // Template file
        NULL
    );
    if (hOutputFile == INVALID_HANDLE_VALUE)
    {
        int lastError = GetLastError();
        std::cerr << "Unable to create the file '" << fileName << "'. [CreateFile] error #" << lastError << "." << std::endl;
    }
    return hOutputFile;
}
DWORD ReadFromFile(HANDLE hFile, void *outData, _UINT64 bytesToRead, _UINT64 location, OVERLAPPED *overlappedPtr, 
    asyncIoCompletionRoutine_t completionRoutine)
{
    DWORD bytesRead = 0;
    if (overlappedPtr)
    {
        // Windows demand that you split the file byte locttion into high & low 32-bit addresses
        overlappedPtr->Offset = (DWORD)_UINT64LO(location);
        overlappedPtr->OffsetHigh = (DWORD)_UINT64HI(location);
        // Should we use a callback function or a manual event
        if (!completionRoutine && !overlappedPtr->hEvent)
        {
            // No manual event supplied, so create one. The caller must reset and close it themselves
            overlappedPtr->hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
            if (!overlappedPtr->hEvent)
            {
                DWORD errNumber = GetLastError();
                std::wcerr << L"Could not create a new event. [CreateEvent] error #" << errNumber << L".";
            }
        }
    }
    BOOL result = completionRoutine ? 
        ReadFileEx(hFile, outData, (DWORD)(bytesToRead), overlappedPtr, completionRoutine) : 
        ReadFile(hFile, outData, (DWORD)(bytesToRead), &bytesRead, overlappedPtr);
    if (result == FALSE)
    {
        DWORD errorCode = GetLastError();
        if (errorCode != ERROR_IO_PENDING)
        {
            std::wcerr << L"Can't read sectors from file. [ReadFile] error #" << errorCode << L".";
        }
    }
    return bytesRead;
}