Data is replicated and stored redundantly over multiple servers for availability in distributed databases. We focus on databases with frequent reads and writes, where both read and write latencies are important. This is in contrast to databases designed primarily for either read or write applications. Redundancy has contrasting effects on read and write latency. Read latency can be reduced by potential parallel access from multiple servers, whereas write latency increases as a larger number of replicas have to be updated. We quantify this tradeoff between read and write latency as a function of redundancy, and provide a closed-form approximation when the request arrival is Poisson and the service is memoryless. We empirically show that this approximation is tight across all ranges of system parameters. Thus, we provide guidelines for redundancy selection in distributed databases.

中文翻译：

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分布式读写系统中的延迟-冗余权衡

数据被复制并冗余存储在多台服务器上，以确保分布式数据库中的可用性。我们专注于频繁读取和写入的数据库，其中读取和写入延迟都很重要。这与主要为读取或写入应用程序设计的数据库形成对比。冗余对读取和写入延迟有不同的影响。读取延迟可以通过来自多个服务器的潜在并行访问来减少，而写入延迟会随着大量副本的更新而增加。我们将读取和写入延迟之间的这种权衡量化为冗余的函数，并在请求到达是泊松且服务无记忆时提供封闭形式的近似值。我们凭经验表明，这种近似在所有系统参数范围内都是严格的。因此，