1、Algorithm
Before rarely do because of problems related algorithms, a little familiar with the database that you select a few questions related to the realization of a database related methods.
182. Find Duplicate e-mail
select Email from Person group by Email having count(Email) > 1
2、Review
http://docs.cloudstack.apache.org/en/4.12.0.0/conceptsandterminology/concepts.html#high-availability
Currently IASS layer of cloud computing cloudstack, Openstack, Zstack (open source people) a few cloud management platform more fire, and we used Zstack in a production environment, before the preliminary understanding through architecture similar Zstack, so I want to look at the Cloudstack official documents and then compare Zstack lower.
1, Allocates v partition assignment 2, Provides provided 3, orchestrates coordination
3, Tip / Techni
Local public cloud SSD disk, SSD disk cloud application scenarios
The company's main business is in the country, the country is based on a hybrid cloud implementation, the core data storage are IDC physical machine storage, all aspects of performance is also good, with the company's strategic development, to develop overseas business, self IDC, the cost is very expensive, so the main use of public cloud to achieve infrastructure, procurement of physical machines 8C 64G 4TSSD local disk for data storage, but found the performance very poor, cloud vendors say that we three identically configured virtual machines on the same physical machine, there is the investigation disk IO contention situation. Then studied at the end of the relevant domestic public cloud leader of the relevant local disk
目前本地SSD盘已经停止售卖。下面内容仅供之前购买过本地SSD盘的用户作参考。 本地SSD盘“本地”是指？ 本地是相对于普通云盘讲的，不同于普通云盘的三份数据副本机制，本地SSD盘采用RAID技术，无法避免单台物理机宕机导致的数据丢失风险；如果您对数据可靠性要求高，则建议在应用层做数据冗余保证数据的可靠性。本地的意思就是没有像普通云磁盘一样的三重备份，采用了RAID技术。 本地SSD盘适合的用户场景有哪些？ 本地SSD盘具有高随机IOPS、高吞吐量、低时延等特点，适合I/O密集型应用，如NoSQL、MPP数据仓库、关系型数据库等场景。 SSD盘相对之前的普通云盘性能提升多少，是否可以提供具体参数？ 数据盘：本地SSD盘相比普通云盘有10~20倍的性能提升，4KB I/O块大小时随机读写IOPS高达12000、512KB I/O块大小时顺序读写吞吐量高达300MB/s。 系统盘：本地SSD盘作为系统盘时，4KB I/O块大小时的随机读写IOPS上限为3000、顺序读写吞吐量上限为80MB/s。 本地SSD盘是否支持在原ECS上进行添加或者将原云磁盘更换成本地SSD盘？ 由于本地SSD盘采用服务器本地盘的方式实现，无法实现远程挂载；因此不支持在原来ECS实例上进行添加本地SSD盘，也不支持将存量的普通云盘更换成本地SSD盘。 购买后是否支持升级？ 由于本地SSD盘采用物理服务器本地盘的方式，购买带有本地SSD盘的实例（包含系统盘和数据盘）无法升级磁盘/CPU/内存等配置，仅支持带宽升级。
4、Share
分享一篇有观点和思考的技术文章
自己写的技术相关文档。
https://blog.51cto.com/dreamlinux/2400404 present written material is relatively monotonous, follow-up and then improve, the theme is a private cloud, public cloud, cloudy,
Share a better read their own documents,
https://tech.sina.com.cn/i/2019-05-25/doc-ihvhiqay1255603.shtml
4、