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Bcache against Flashcache for Ceph Object Storage

Reading time 11 min
Views 2.5K

Fast SSDs are getting cheaper every year, but they are still smaller and more expensive than traditional HDD drives. But HDDs have much higher latency and are easily saturated. However, we want to achieve low latency for the storage system, and a high capacity too. There’s a well-known practice of optimizing performance for big and slow devices — caching. As most of the data on a disk is not accessed most of the time but some percentage of it is accessed frequently, we can achieve a higher quality of service by using a small cache.

Server hardware and operating systems have a lot of caches working on different levels. Linux has a page cache for block devices, a dirent cache and an inode cache on the filesystem layer. Disks have their own cache inside. CPUs have caches. So, why not add one more persistent cache layer for a slow disk?
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Total votes 16: ↑16 and ↓0 +16
Comments 0

How Many Developers Need to Create Service Like Airbnb

Reading time 4 min
Views 3K
Back in 2007, Brian Chesky and Joe Gebbia shared a room in San Francisco and were unable to pay rent on time. As a way out, they decided to turn their living space into a simple bed-and-breakfast hotel to get some money from travelers. If you love traveling i can advice you Travel news site. A year later, the venturers launched a website which evolved into the most famous peer-to-peer renting technology service called Airbnb.

 Now, the company has 3,100 employees and generates insane revenues for its founders. The statistics say that Airbnb has 150 million registered users, 3 million hosts, and 4 million listed offers. The service covers 80,000 cities in 190 countries, and, interestingly, 50% of traffic comes from mobile applications.

  These figures are so impressive that you may also want to create your own Airbnb clone and become successful. But slow down. This story is already written; do you really need to create a marketplace similar to Airbnb?
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Total votes 14: ↑13 and ↓1 +12
Comments 0

How Protonmail is getting censored by FSB in Russia

Reading time 10 min
Views 8.4K

A completely routine tech support ticket has uncovered unexpected bans of IP addresses of Protonmail — a very useful service for people valuing their Internet freedoms — in several regions of Russia. I seriously didn’t want to sensationalize the headline, but the story is so strange and inexplicable I couldn’t resist.


TL;DR


Disclaimer: the situation is still developing. There might not be anything malicious, but most likely there is. I will update the post once new information comes through.


MTS and Rostelecom — two of the biggest Russian ISPs — started to block traffic to SMTP servers of the encrypted email service Protonmail according to an FSB request, with no regard for the official government registry of restricted websites. It seems like it’s been happening for a while, but no one paid special attention to it. Until now.


All involved parties have received relevant requests for information which they’re obligated to reply.


UPD: MTS has provided a scan of the FSB letter, which is the basis for restricting the access. Justification: the ongoing Universiade in Krasnoyarsk and “phone terrorism”. It’s supposed to prevent ProtonMail emails from going to emergency addresses of security services and schools.


UPD: Protonmail was surprised by “these strange Russians” and their methods for battling fraud abuse, as well as suggested a more effective way to do it — via abuse mailbox.


UPD: FSB’s justification doesn’t appear to be true: the bans broke ProtonMail’s incoming mail, rather than outgoing.


UPD: Protonmail shrugged and changed the IP addresses of their MXs taking them out of the blocking after that particular FSB letter. What will happen next is open ended question.


UPD: Apparently, such letter was not the only one and there is still a set of IP addresses of VOIP-services which are blocked without appropriate records in the official registry of restricted websites.

Total votes 66: ↑64 and ↓2 +62
Comments 4

Writing yet another Kubernetes templating tool

Reading time 8 min
Views 12K


If you are working with Kubernetes environment then you probably make use of several existing templating tools, some of them being a part of package managers such as Helm or Ksonnet, or just templating languages (Jinja2, Go template etc.). All of them have their own drawbacks as well as advantages and we are going to go through them and write our own tool that will try to combine the best features.

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Total votes 22: ↑21 and ↓1 +20
Comments 1

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