SSD 性能参数 - 延迟与 IOPS？
SSD performance parameters - latency vs IOPS?
最常用的 SSD 性能指标据说是：吞吐量 (MBps)、IOPS 和延迟 (ms)。我对后两者有点困惑，因为：
- IOPS - 测量每完成多少输入输出操作
第二
- latency - 完成一个IO操作需要多长时间
从头到尾
（从这里获取定义：https://www.custompcreview.com/articles/iops-throuhput-latency-understanding-ssd-hdd-storage-performance-benchmarks/）
因此，如果延迟定义了 I/O 操作的处理持续时间，我会天真地得出结论 IOPS = 1/延迟（至少对于深度队列 = 1）。但事实显然并非如此。那么这里有什么区别呢？
我知道 SSD 受益于大队列深度（并发 I/O 操作的数量），但即使这些操作是并发的，每秒 I/O 操作的总数也会与 I/O 延迟，不是吗？
我会从这里引用，因为这篇文章回答了你所需要的：
https://storageswiss.com/2013/12/10/what-is-latency-and-how-is-it-different-from-iops/
In order to maintain IOPS performance storage systems need enough
pending requests for data be available (in a queue) so that the
latencies of a few individual requests don’t adversely impact the
overall IOPS performance of the system. When queue depths are low,
latency becomes a larger determinant of storage performance and in
flash based storage systems, low (or no) queue depth is a common
occurrence.
While adequate transaction queues are required to realize SSD
performance, large queue depths can actually mask latency in the short
run. Essentially, the system can process a large number of
transactions per second from the queue (high IOPS) but still take a
relatively long time to complete those transactions (long latency).
So, in the short-term IOPS may look good, even though the system’s
ability to improve performance in the long-term is poor. For these
reasons, latency is often a more important metric than IOPS for
measuring SSD system performance.
总结：延迟会影响 IOPS，但不会以一致的方式影响。因此，它被视为 SSD 的另一种衡量标准，仅次于 IOPS。
最常用的 SSD 性能指标据说是：吞吐量 (MBps)、IOPS 和延迟 (ms)。我对后两者有点困惑，因为：
- IOPS - 测量每完成多少输入输出操作 第二
- latency - 完成一个IO操作需要多长时间 从头到尾
（从这里获取定义：https://www.custompcreview.com/articles/iops-throuhput-latency-understanding-ssd-hdd-storage-performance-benchmarks/） 因此，如果延迟定义了 I/O 操作的处理持续时间，我会天真地得出结论 IOPS = 1/延迟（至少对于深度队列 = 1）。但事实显然并非如此。那么这里有什么区别呢？ 我知道 SSD 受益于大队列深度（并发 I/O 操作的数量），但即使这些操作是并发的，每秒 I/O 操作的总数也会与 I/O 延迟，不是吗？
我会从这里引用，因为这篇文章回答了你所需要的： https://storageswiss.com/2013/12/10/what-is-latency-and-how-is-it-different-from-iops/
In order to maintain IOPS performance storage systems need enough pending requests for data be available (in a queue) so that the latencies of a few individual requests don’t adversely impact the overall IOPS performance of the system. When queue depths are low, latency becomes a larger determinant of storage performance and in flash based storage systems, low (or no) queue depth is a common occurrence.
While adequate transaction queues are required to realize SSD performance, large queue depths can actually mask latency in the short run. Essentially, the system can process a large number of transactions per second from the queue (high IOPS) but still take a relatively long time to complete those transactions (long latency). So, in the short-term IOPS may look good, even though the system’s ability to improve performance in the long-term is poor. For these reasons, latency is often a more important metric than IOPS for measuring SSD system performance.
总结：延迟会影响 IOPS，但不会以一致的方式影响。因此，它被视为 SSD 的另一种衡量标准，仅次于 IOPS。