3 ms·

Pedantry -- that isn't Moore's Law related, aside from the loosest interpretation that computers as a whole get faster. This is so true, though. Much of the ho

Pedantry -- that isn't Moore's Law related, aside from the loosest interpretation that computers as a whole get faster. This is so true, though. Much of the horizontally scalability need comes from the land of extremely underpowered VPS machines on platforms like AWS. Yet the mind-boggling scale of performance you can inexpensively* (*-term used relatively) acquire for database servers is astonishing. SSDs (and plug-in flash drives) and boundless memory have changed everything.

masklinn 15y ago
> Pedantry -- that isn't Moore's Law related Actually, RAM would be the perfect application of the exact meaning of Moore's law: more RAM is an almost direct function of more transistors, and Moore's law is: > the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years Moore's law precisely predicts you can double your amount of RAM every two years for the exact same price. Which is pretty much what TFA is about. SSD storage size is the same thing.
_delirium 15y ago
Given all the problems they've had with AWS, I wonder what the overall cost/benefit would be for someone like Reddit moving from the flexed-EC2-servers model to just one high-powered db server and some caching webservers in front of it.
- adestefan 15y ago
  Reddit's probably was using trying to use EBS as a backend for a transactional database. The issue is that EBS makes no guarantees on latency, only that they'll never lose your data.
  - bad_user 15y ago
    they'll never lose your data Amazon is not saying it, but EBS is probably lying when doing an fsync(). In this post [1] explaining why Reddit was down, one problem was that the DB slave got ahead of the master, with the most probable explanation being that the master flagged the data as being safe for replication, before committing it to disk and I trust PostgreSQL more than I trust EBS. In this forum answer Amazon is giving about this potential problem [2], they are dodging the question by saying that fsync() guarantees durability for instance failures, but not for volume failures, with the anual failure rate (AFR) being given as 0.1% - 0.5% for volumes (how accurate that is, it remains to be seen). So EBS is probably lying about fsync's success, especially since the behavior of fsync in virtual environments is always a surprise. So you can definitely lose your data more frequently than if you had your own hardware. [1] blog.reddit.com/2011/03/why-reddit-was-down-for-6-of-last-24.html [2] https://forums.aws.amazon.com/thread.jspa?threadID=27590 https://forums.aws.amazon.com/thread.jspa?threadID=27590
    - cperciva 15y ago
      Amazon is not saying it, but EBS is probably lying when doing an fsync(). Given that POSIX says "the nature of the transfer is implementation-defined" and they've defined what fsync does on their implementation: No, they're not lying. I wouldn't say that they're being misleading, either. On a local physical disk, once fsync returns your data is safely stored unless/until the disk dies. According to the forum post you linked to, semantics on EBS are exactly the same. fsync does not mean "has been written to spinning magnetic media".
  - deleted 15y ago
    [deleted]
  - pangram 15y ago
    Reddit also found EBS to be unreliable; they've moved all their high traffic data to ephemeral storage. They have an interesting summary of their technology stack here: http://blog.reddit.com/2012/01/january-2012-state-of-servers.html http://blog.reddit.com/2012/01/january-2012-state-of-servers...
- foobarbazetc 15y ago
  Reddit could easily cut their spend on hosting by like 50-75% just by moving to a dedicated hosting provider. They'd also get bare metal speeds in the process. Who knows why they've stuck with AWS, though. It's possible Amazon is giving them a discount so they can be used as an example.

masklinn 15y ago

> Pedantry -- that isn't Moore's Law related Actually, RAM would be the perfect application of the exact meaning of Moore's law: more RAM is an almost direct function of more transistors, and Moore's law is: > the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years Moore's law precisely predicts you can double your amount of RAM every two years for the exact same price. Which is pretty much what TFA is about. SSD storage size is the same thing.

_delirium 15y ago

Given all the problems they've had with AWS, I wonder what the overall cost/benefit would be for someone like Reddit moving from the flexed-EC2-servers model to just one high-powered db server and some caching webservers in front of it.

adestefan 15y ago
Reddit's probably was using trying to use EBS as a backend for a transactional database. The issue is that EBS makes no guarantees on latency, only that they'll never lose your data.
- bad_user 15y ago
  they'll never lose your data Amazon is not saying it, but EBS is probably lying when doing an fsync(). In this post [1] explaining why Reddit was down, one problem was that the DB slave got ahead of the master, with the most probable explanation being that the master flagged the data as being safe for replication, before committing it to disk and I trust PostgreSQL more than I trust EBS. In this forum answer Amazon is giving about this potential problem [2], they are dodging the question by saying that fsync() guarantees durability for instance failures, but not for volume failures, with the anual failure rate (AFR) being given as 0.1% - 0.5% for volumes (how accurate that is, it remains to be seen). So EBS is probably lying about fsync's success, especially since the behavior of fsync in virtual environments is always a surprise. So you can definitely lose your data more frequently than if you had your own hardware. [1] blog.reddit.com/2011/03/why-reddit-was-down-for-6-of-last-24.html [2] https://forums.aws.amazon.com/thread.jspa?threadID=27590 https://forums.aws.amazon.com/thread.jspa?threadID=27590
  - cperciva 15y ago
    Amazon is not saying it, but EBS is probably lying when doing an fsync(). Given that POSIX says "the nature of the transfer is implementation-defined" and they've defined what fsync does on their implementation: No, they're not lying. I wouldn't say that they're being misleading, either. On a local physical disk, once fsync returns your data is safely stored unless/until the disk dies. According to the forum post you linked to, semantics on EBS are exactly the same. fsync does not mean "has been written to spinning magnetic media".
- deleted 15y ago
  [deleted]
- pangram 15y ago
  Reddit also found EBS to be unreliable; they've moved all their high traffic data to ephemeral storage. They have an interesting summary of their technology stack here: http://blog.reddit.com/2012/01/january-2012-state-of-servers.html http://blog.reddit.com/2012/01/january-2012-state-of-servers...
foobarbazetc 15y ago
Reddit could easily cut their spend on hosting by like 50-75% just by moving to a dedicated hosting provider. They'd also get bare metal speeds in the process. Who knows why they've stuck with AWS, though. It's possible Amazon is giving them a discount so they can be used as an example.