因为“在BigTable里数据可能放在任何地方[……]，平均读取时间可能相对较高”。

Since "in BigTable data can be anywhere [...] the average retrieval time can be relatively high". You trade speed against scalability.

youdao

不过，我们最关心的是平均读取时间。 在我们的基础测试中平均读取时间为 6.3 MB/秒，而读操作的速度为 4.3 MB/秒左右。

The key element we are concerned with, though, is the average read time, and in our base testing we obtained 6.3 MB per second, with about 4.3 MB of that being read operations.

youdao

所有版本均配备8 MB的缓冲，他们正在与3.5毫秒，4.0毫秒的平均读取寻道时间额定平均写。

All versions are equipped with 8 MB buffer and they're rated with 3.5 ms average read and 4.0 ms average write seek time.

youdao