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As larger and larger amount of memory become common (512GB is something you can fit into relatively commodity server this day) many customers select to build their application so all or most of their database (frequently Innodb) fits into memory.

If all tables fit in Innodb buffer pool the performance for reads will be quite good however writes will still suffer because Innodb will do a lot of random IO during fuzzy checkpoint operation which often will become bottleneck. This problem makes some customers not concerned with persistence run Innodb of ram drive

In fact with relatively simple changes Innodb could be made to perform much better for memory resident workloads and we should consider fixing these issues for XTRADB.

Preload It is possible to preload all innodb tables (ibdata, .ibd files) on the system start - this would avoid warmup problem and also make crash recovery fast even with very large log file - random IO is what usually limits recovery speed. Because files can be just read sequentially the read speed can be hundreds of megabytes per second even for commodity RAIDs.

Sequential Checkpointing Currently fuzzy checkpoint flushes pages which have not been flushed for longest amount of time which causes random IO. In resident checkpoint mode we should just flush everything (yes even clean pages) sequentially. This should allow to get sequential writes giving us 100MB+ of write speed - which means 256GB buffer pool can be flushed about once per 30 minutes. It should be possible to just size Innodb logs so they are not cycled through faster than flush cycle.

This may not be the most optimal solution if you design the system from scratch but it is something which can be done without changing Innodb core logic significantly or storing on disk storage format at all.

This is just an idea at this point which I’ve discussed with some customers and we’re not working on it yet, though if you think it is something which you think would help your performance challenges we would be happy to implement it for you.

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Entry posted by peter | No comment

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举办社会企业家技能培训的友成基金会现在推出了他们的blog: 友成@YouChange，他们使用了一个很棒的品牌名称：YouChange

网址：
http://youchange.org.cn
RSS订阅地址：
http://youchange.org.cn/?feed=rss2

这里有一篇值得一看的文章：《绿色回声主席Cheryl Dorsey谈社会企业家精神》，绿色回声（Echoing Green）和它的主席Cheryl Dorsey就是提供和建立社会企业家精神支持体系的典范之一。Cheryl是第一个成为该组织主席的绿色回声Fellow。她在Reynolds项目的活动现场发表了演讲，分享了她对社会企业家的见解。

Cheryl Dorsey的相片

Cheryl Dorsey提到:

写The Tipping point (引爆流行)的作者Malcolm Gladwell在书中提到，社会变革不是由那些拥有强大政治或者金钱权利的人带来的，真正带来社会变革的是有强大社会力量的连接者。他们是很好的桥梁搭建者，深入不同群体，组织和动员大量的社会力量带来社会改变。

Cheryl Dorsey是在参加纽约大学的Reynolds 社会企业家精神项目时发表了这个演讲。这个Reynolds活动本身也很有意思。它旨在吸引三种社会变革者：

一： “传统”意义的变革者，也就是直接做事情带来改变的人；
二： 那些建立和维护基础构架的人，比如为变革者提供知识、资源、法律等服务的人，以及建立支持体系组织的人；
三： 为社会企业家精神做倡导和宣传的人，摄影师、编剧、导演、音乐、话剧、纪录片等等。

Reynolds项目相信，行动的多方法和多元化对发起任何一项运动、带动整个社会的关注和行动都是至关重要的。该项目向每年获选的本科及研究生学员提供培训、咨询、网络资源以及终身的跟进支持。

社会化网络实际上提供了一个环境，让三类社会变革者互相联系得更紧密，也在模糊彼此的活动领域和角色定义。直接做事，在实践前沿的朋友，可以透过社会化网络分享他们的实验心得，分享他们的模式，建立志愿者社区，输出品牌。这些工作，实际上也是在为后来者建立基础构架，只是这个基础构架一开始就是开放式的生态系统，它会自然演化和拓展，而不是固定在一个小范围内自生自灭。

那些幕后英雄和布道者，他们的所作所为，又何尝不是在做具体的事情呢？！从某种意义上说，中国大陆甚至更需要更多的幕后英雄和布道者，这样才有可能催生更大规模的社会变革者群体。

阿育王（Ashoka）的代表最近访问友成北京办公室，他们早先已经有过多次接触，双方将在社会企业家精神传播、知识积累和网络分享方面开展合作，Ashoka方面将向友成提供更多适合中国的相关书籍、文章和案例。

看来，今后友成的这个blog将有很多精彩的内容，感兴趣的朋友，现在可以留心订阅。