http://arstechnica.com/information-technology/2014/10/scare-your-neighbors-with-a-spooky-halloween-network-name/ удобно

We’ve chosen to use the terms “primary” and “replica” in discussing Redis, rather than the terms “master” and “slave” used in the Redis documentation, to support inclusivity. For some interesting and heated discussion of this substitution, we’d recommend this Django pull request and this Drupal change.

Because scoring-srv is latency-sensitive, we had configured the primary node not to snapshot its data to disk. Instead, the two replicas each made frequent snapshots. In the case of failure of the primary, we expected one of the two replicas to be promoted to primary; when the failed process came back up, we expected it to restore its data via replication from the new primary. That didn’t happen. Instead, when we ran kill -9 on the primary node (and it was restarted by daemontools), it came back up – after, again, flapping for a short time – with no data, but was still acting as primary. From there, it restarted replication and sent its empty dataset to the two replica nodes, which lost their datasets as a result. In a few seconds, we’d gone from a three-node replicated data store to an empty data set.

So Arista has a switch with an FPGA - 7124FX. The market for the HFT has crashed. When Arista shipped the 7124S the HFT guys where using Cisco 4900 at 4ms and the 7124S was at 600ns. It was quite a change. The markets went crazy. The chip was called Bali by Fulcrum Microsystems - Intel bought them. The follow on chip Alta was very very very late. Arista did the 7124SX which got the latency down to 500ns. The Bali itself was 300ns but the PHY chips added the additional latency (in and out). This switch replaced the 7124S but there was not a mad rush to upgrade. Going from 4ms to 600ns was an order of magnitude but going from 600ns to 500ns, not so much. Cisco who got killed by Arista in this market spent ~$100M and came up with the Nexus 3548. It had "warp mode" that could do ~50ns. This mode however required lots of pre-planning and was fixed. Market data feeds are multicast. The handoff from the exchange was 1G or even low as 100mb in the Asian markets back then. If you added up every feed you could buy it was around ~3G. You would never do this on one link. The servers for looking at the data would join groups to get the feed. The servers used 10G NICs when the traffic load on them was only around ~100MB. Once again for latency. Serialization delay was the key here. The market order would go back up to the market on another path. The idea was the HFT guys would want to process the data faster then the rest of the people. The link down to them and the link up to order was the same for everyone. If you went into the NYSE colo the cable length to the router was the same if you where in the rack next to it or on the other side of the datacenter. Anyway back to switches. So Arista shipped the 7150 around the same time as Cisco shipped the 3548. It was around 350ns using the Alta chip. The reality was that this was low enough and the traders started to look for other places to tweak.

http://tinytocs.org удобно // свежо

Моя проблема знакома многим девушкам. Мой муж не хочет работать. Его любимое занятие - поиграть в компьютерные игры. За год он может поработать пару месяцев, остальное время сидит дома, мне врет, что ищет работу. При этом он не любит в чем-то себе отказывать. Курит дорогие сигареты, любит вкусно поесть, покупает дорогие вещи и обувь. Моей зарплаты катастрофически не хватает, у нас есть несколько кредитов, оформленных на меня. Почему я не ухожу от него? Да потому что жду, когда он устроится на работу и закроет хотя бы часть кредитов, одна я буду расплачиваться долго. Он может заработать приличную сумму и погасить хоть один кредит за короткое время, такое уже было. Когда он работает, мы живем отлично. В остальное время чуть ли не голодаем. Сейчас он не работает уже три месяца, на день рождения мне не подарил даже дешевого букета. В октябре я хожу по улице в балетках, нет денег на сапоги. Он же взял у родителей денег и идет покупать себе ботинки, т.к.на старых потрескался нос!

Отныне слово „украинец“ для нас самое страшное проклятье. Отныне слово „украинец“ разряжает ружье. Не будем говорить. Не будем возмущаться. Будем убивать.

Скиньте статью камара про то как научиться писать на руби

http://www.meetup.com/DevOps-Moscow-in-Russian/events/214753582/comments/435350012/ деанон