Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Amazon Time Sync Service

aws.amazon.com

Post reply on HN
Print view View original

51–60 of 94 posts

Re: Amazon Time Sync Service

#51

Post by quin3 »

rp1 wrote: post #33
mrep wrote: post #16

Earlier quoted context omitted.

I'm not sure how you think a distributed data processing technology would "fake-out" other companies when building/choosing database technology. They are totally different problem sets. MapReduce does not have a set in stone data source/sink and can use multiple things like bigtable and spanner so they are complementary technologies.

I think the parent commenter might be referring to systems like Hive or HBase built on top of Hadoop and do have a lot of overlap with a large scale database system.

HBase isn’t really related to MapReduce though, more akin to BigTable.

Re: Amazon Time Sync Service

#52

Post by NavinF »

deelowe wrote: post #49
loxias wrote: post #39

Two observations/questions, the first probably naive: * It's not that hard to get your own "world class" time server, for under a thousand. A Rb standard slaved to a GPSDO is gonna be so accurate and stable, and use that to drive a SBC that supports IEEE1588, where you run your NTP and PTP server. Oh, but I guess that box, while inexpensive, isn't in Amazons DC, so doesn't help you. * PTP's absence in the Amazon Time…

Amazon time sync likely also requires extremely accurate clocks on the system board as well to prevent there from being too much drift.

You don’t even need a tcxo. If you don’t care about holdover, connecting the pps pin from a $5 GPS module to an $15 SBC will give you a time source that is significantly better than anything you can serve over NTP to your clients. NTP is always gonna be the weak link for a service like this.

Re: Amazon Time Sync Service

#53

Post by travisgriggs »

loxias wrote: post #43
Gelob wrote: post #41

Earlier quoted context omitted.

Them providing PTP would be really interesting

To be clear, what I meant was "the fact that they're advertising whiz bang time synchronization, but then not using the correct protocol, makes me question the quality of the whole enterprise". Even on local networks, NTP can only get you so close. If you set up chrony just so, in ideal conditions, I've gotten hundreds of microseconds (more commonly ~500-1000us). But combined with PTP, you can get sub-microsecond acc…

When Microsoft did that kind of thing we called it “embrace and extend.”

Re: Amazon Time Sync Service

#55

Post by glenngillen »

Back from my time at Amazon, one of my favourite technical videos on the internal educational/YouTube thing was from a service team explaining how hard accurate clock sync in distributed systems was. One of those problems I’ve just taken for granted over the years. But just layers and layers of complexity where naive assumptions at any point get you the wrong result, but it’s not at all obvious you have the wrong result.

I really wish they made more of that stuff publicly available.

Re: Amazon Time Sync Service

#58

Post by deelowe »

NavinF wrote: post #52
deelowe wrote: post #49

Earlier quoted context omitted.

Amazon time sync likely also requires extremely accurate clocks on the system board as well to prevent there from being too much drift.

You don’t even need a tcxo. If you don’t care about holdover, connecting the pps pin from a $5 GPS module to an $15 SBC will give you a time source that is significantly better than anything you can serve over NTP to your clients. NTP is always gonna be the weak link for a service like this.

I was referring to the amazon time sync service which I imagine has pretty tight timing requirements (similar to spanner), not NTP.

Also, how exactly would GPS work at scale for 10,000s of servers within 1000s of racks within a DC?

Re: Amazon Time Sync Service

#59

Post by jfrunyon »

deelowe wrote: post #58
NavinF wrote: post #52

Earlier quoted context omitted.

You don’t even need a tcxo. If you don’t care about holdover, connecting the pps pin from a $5 GPS module to an $15 SBC will give you a time source that is significantly better than anything you can serve over NTP to your clients. NTP is always gonna be the weak link for a service like this.

I was referring to the amazon time sync service which I imagine has pretty tight timing requirements (similar to spanner), not NTP. Also, how exactly would GPS work at scale for 10,000s of servers within 1000s of racks within a DC?

"Amazon provides the Amazon Time Sync Service, which is accessible from all EC2 instances, and is also used by other AWS services. This service uses a fleet of satellite-connected and atomic reference clocks in each AWS Region to deliver accurate current time readings of the Coordinated Universal Time (UTC) global standard through Network Time Protocol (NTP). The Amazon Time Sync Service automatically smooths any leap seconds that are added to UTC.

"The Amazon Time Sync Service is available through NTP"

https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/set-time...

Re: Amazon Time Sync Service

#60

Post by jfrunyon »

bogomipz wrote: post #48
Groxx wrote: post #37

Earlier quoted context omitted.

Time is hard. By asking both super-microscopic stuff and stuff way out in space, you can now find out what time it is!

One is cesium? Whats the other stuff, way out in space?

Rubidium. Cesium atomic clocks are more expensive.
Post reply on HN