您好，请教下 bcache做缓存后，宿主机上测试bcache随机写确实性能很好，但是用qemu-KVM创建虚机运行在bcache0 设备上，结果测试顺序写和随机写不正常
randread 8k: read: IOPS=20.9k, BW=163MiB/s (171MB/s)(3265MiB/20002msec)
randread 16k: read: IOPS=16.3k, BW=253MiB/s (266MB/s)(5068MiB/20001msec)
randread 32k: read: IOPS=11.5k, BW=357MiB/s (374MB/s)(7144MiB/20003msec)
randread 64k: read: IOPS=6978, BW=436MiB/s (457MB/s)(8192MiB/18782msec)
randread 1024k: read: IOPS=525, BW=525MiB/s (551MB/s)(8192MiB/15597msec)
randwrite 8k: write: IOPS=12, BW=101KiB/s (104kB/s)(2344KiB/23170msec)
randwrite 16k: write: IOPS=12, BW=194KiB/s (198kB/s)(4352KiB/22471msec)
randwrite 32k: write: IOPS=13, BW=417KiB/s (427kB/s)(9408KiB/22554msec)
randwrite 64k: write: IOPS=13, BW=842KiB/s (862kB/s)(18.9MiB/22890msec)
randwrite 1024k: write: IOPS=12, BW=12.6MiB/s (13.2MB/s)(281MiB/22432msec)
randrw 8k:
read: IOPS=28, BW=229KiB/s (234kB/s)(4944KiB/21621msec)
write: IOPS=12, BW=104KiB/s (106kB/s)(2248KiB/21621msec)
randrw 16k:
read: IOPS=29, BW=464KiB/s (476kB/s)(9.85MiB/21668msec)
write: IOPS=13, BW=213KiB/s (218kB/s)(4608KiB/21668msec)

老大你好，最近在配置阿里云CentOS7上的postfix，想使用外部SMTP发送邮件，看到您的博文《配置 Postfix 通过外部 SMTP 服务器发邮件》（https://blog.lilydjwg.me/2016/5/29/send-mail-with-postfix-via-external-smtp-server.201522.html），其中配置main.cf里的配置时，有一个smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt，请问这个证书要如何获得呢？能否赐教，谢谢~~我的邮箱：mytino@126.com

贵站的关于页面是我见过最有创意的

仙子大佬你好，我是在解决一个bug的时候，无意中在segmentfault网站找到了你回答的答案，非常感谢的解答让我解决了这个bug。

Hello,

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Product Marketing Manager
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自我介绍怎么这么靓呢?!目前见过的最创意、最英气，star star

这个blog背景图片在1920×1800分辨率下左右会有白边，因为不够大
改成 background: #FFF url("../images/default.jpg") fixed bottom / cover; 似乎可以拉伸到合适大小

仙子，移动版支持好差，怎么办~~