选择Redis最大内存大小和BGSAVE内存使用情况 [英] Choosing redis maxmemory size and BGSAVE memory usage

问题描述

我正在尝试找出在以下情况下"maxmemory"的安全设置:

I am trying to find out what a safe setting for 'maxmemory' would be in the following situation:

• 繁重的应用程序
• 8GB RAM
• 假设其他进程占用约1GB
• 这意味着redis进程的内存使用量不得超过7GB
• 在每个BGSAVE事件中，内存使用量都会增加一倍，原因是:

在redis docs 中，有关BGSAVE事件的内存使用量增加的说法如下:

In the redis docs the following is said about the memory usage increasing on BGSAVE events:

如果要在写入量很大的应用程序中使用Redis，则在将RDB文件保存在磁盘上或重写AOF日志的同时，Redis最多可能会使用通常使用的内存的2倍.

If you are using Redis in a very write-heavy application, while saving an RDB file on disk or rewriting the AOF log Redis may use up to 2 times the memory normally used.

• 将最大内存限制与redis-cli INFO中的'used_memory'进行了粗略比较(如我是否更正，这意味着在这种情况下，最大内存设置应该设置为不大于(8GB-1GB)/2 = 3.5GB?

  Am I correct that this means that the maxmemory setting should, in this situation, be set no higher than (8GB - 1GB) / 2 = 3.5GB?

  如果是这样，我将为redis文档创建拉取请求，以更清楚地反映这一点.

  If so, I will create a pull request for the redis docs to reflect this more clearly.

  推荐答案

  在这种情况下，我建议限制为3GB.是的，文档非常正确，短期内运行bgsave会使内存需求增加一倍.但是，我更愿意为系统保留2GB的内存，或者为永久主机保留的最大内存为最大内存的40％.

  I would recommend in this case a limit of 3GB. Yes, the docs are pretty much correct and running a bgsave will double for a short term the memory requirements. However, I prefer to reserve 2GB of memory for the system, or at a maximum for a persisting master 40% of maximum memory.

  您表示您的应用程序写得很繁重.在这种情况下，我强烈建议第二台服务器执行保存操作.我发现在大量写入和bgsave期间，对客户端的响应时间会变长.不是Redis本身引起的，而是服务器本身的响应.对于虚拟机尤其如此.在此设置下，您将使用第二台服务器从主服务器作为从服务器并保存到磁盘，而第一台服务器保持响应.

  You indicate you have a very write heavy application. In this case I would highly recommend a second server do the save operations. I've found during high writes and a bgsave the response time to the client(s) can get high. It isn't Redis per se causing it, but the response of the server itself. This is especially true for virtual machines. Under this setup you would use the second server to slave from the primary and save to disk while the first remains responsive.

  这篇关于选择Redis最大内存大小和BGSAVE内存使用情况的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！