Comment by osivertsson
9 days ago
Laws of physics hasn't changed since the early 00s though, we could build very low latency point to point links back then too.
9 days ago
Laws of physics hasn't changed since the early 00s though, we could build very low latency point to point links back then too.
Switching gear was slower and laying new fibre wasn't an option for your average company. Particularly not point-to-point between your DB server and your replica.
So if real-time synchronization isn't practical, you are then left to do out-of-hours backups and there you start running into bandwidth issues of the time.
Never underestimate the potential packet loss of a Concorde filled with DVDs.
Plus long distance was mostly fibre already. And even regular electrical wires aren’t really much slower than fibre in term of latency. Parent probably meant bandwidth.
Copper doesn't work over these kinds of distances without powered switches, which adds latency. And laying fibre over several miles would be massively expensive. Well outside the realm of all but the largest of corporations. There's a reason buildings with high bandwidth constraints huddle near internet backbones.
What used to happen (and still does as far as I know, but I've been out of the networking game for a while now) is you'd get fibre laid between yourself and your ISP. So you're then subject to the latency of their networking stack. And that becomes a huge problem if you want to do any real-time work like DB replicas.
The only way to do automated off-site backups was via overnight snapshots. And you're then running into the bandwidth constraints of the era.
What most businesses ended up doing was tape backups and then physically driving it to another site -- ideally then storing it an fireproof safe. Only the largest companies could afford to push it over fibre.
To be fair, tape backups are very much ok as a disaster recovery solution. It's cheap once you have the tape drive. Bandwith is mostly fine if you want to read them sequentially. It's easy to store and handle and fairly resistant.
It's "only" poor if you need to restore some files in the middle or want your backup to act as a failover solution to minimise unavailability. But as a last resort solution in case of total destruction, it's pretty much unbeatable cost-wise.
G-Drive was apparently storing less than 1PB of data. That's less than 100 tapes. I guess some files were fairly stable so completely manageable with a dozen of tape drives, delta storage and proper rotation. We are talking of a budget of what 50k$ to 100k$. That's peanuts for a project of this size. Plus the tech has existed for ages and I guess you can find plenty of former data center employees with experience handling this kind of setup. They really have no excuse.
2 replies →
> There's a reason buildings with high bandwidth constraints huddle near internet backbones.
Yeah because interaction latency matters and legacy/already buried fiber is expensive to rent so you might as well put the facility in range of (not-yet-expensive) 20km optics.
> Copper doesn't work over these kinds of distances without powered switches, which adds latency.
You need a retimer, which adds on the order of 5~20 bits of latency.
> And that becomes a huge problem if you want to do any real-time work like DB replicas.
Almost no application would actually require "zero lost data", so you could get away with streaming a WAL or other form of reliably-replayable transaction log and cap it to an acceptable number of milliseconds of data loss window before applying blocking back pressure. Usually it'd be easy to tolerate enough for the around 3 RTTs you'd really want to keep to cover all usual packet loss without triggering back pressure.
Sure, such a setup isn't cheap, but it's (for a long while now) cheaper than manually fixing the data from the day your primary burned down.
Yes but good luck trying to get funding approval. There is a funny saying that wealthy people don't become wealthy by giving their wealth away. I think it applies to companies even more.