alt Hacker NewsThat is actually surprising to me. Claims like that are pretty common, they make sense and they should be true, so even though I don't really know AWS (/Backblaze/Azure/whatever) redundancy planning in enough detail, I used to trust them. It's really worrying when they outright say it will be ok, and then a week later it turns out to be not ok.
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Well, listen, you do know that even when the largest most ambitious and most sophisticated things are shipped, each owner of each specific part (could be many many owners) basically , to the best of their ability, prayed that nothing particularly bad happens when it’s shipped off. Truly, that’s the best a mortal human can do, pray their part doesn’t break.
So then that big thing comes to you. It’s all kind of … held together by a prayer …
Trust me I’ve worked at these big places. You wouldn’t believe how much fucking luck and grace from God is allowing you to do anything with your digital life. It’s a mindfuck of a tangled mess out there, eternities worth of written code that only God ensures works together at this point, only to get more hidden with AI.
It really is important to understand the failure modes that the durability model accounts for and what it doesn't. It only accounts for "normal" failures, like an HDD reaching end of life.
For example, you mention Backblaze. Backblaze has public posts about their durability model. They claim to use 17:20 Reed-Solomon erasure encoding. That means there are 20 shards of a blob, and you can lose 3 of them and still reconstruct the blob.
Think about that for a second. If they store 4 shards in a datacenter, that means that a loss of that one datacenter is sufficient to lose the blob, forever. That entails that blobs are sharded across a minimum of 7 data centers, or the loss of one data center might mean permanent data loss. Which one do you think is true? (In fact it's pretty clear from Backblaze's public posts that they don't shard across data centers at all, only across racks within a data center.)
Now, AWS's availability guarantee — not their durability guarantee — entails that they use a less cost-effective erasure coding ratio. S3 is designed so that your blob is available even if a whole AZ goes down, and it's well known that most AWS regions have only 3 AZs. Therefore, if you tolerate the same number of shards lost to HDD failure as Backblaze in your durability model (3), then you might need 17:30 erasure coding to get the same durability and the required availability. That means S3 is storing way more physical bytes than Backblaze — 1.76x the logical size of the blob, instead of Backblaze's 1.18x. That's more expensive, but it also gives you better availability.
Which is also why One Zone S3 is cheaper — if you don't care about the availability guarantee, S3 can do what Backblaze does and save 33% on physical bytes, and they pass on 40–50% of those savings to the customer (this is fairer than it sounds — there's more overhead than physical storage bytes).
But here's the thing. AWS has more redundancy built in than Backblaze because they make availability guarantees in addition to durability guarantees. BUT the durability model is the same, which is why Backblaze can claim equivalent durability to S3. S3 in fact has better durability — they can survive the permanent loss of an AZ without necessarily losing blobs stored there (with the exception of One Zone blobs), and Backblaze cannot. But that's not actually a factor of the durability model, which is just taking into account normal events like HDD failure. Instead, S3 has durability that's more resilient to AZ loss because of their availability model. It's a side effect that isn't actually part of the durability promise!
The caveat is always "if you're using the service correctly" which is not necessarily free. Meaning taking advantage of multiple geo zones, building in redundancy to your stack, etc. Like everything he said is possible if your technology stack living in AWS was designed to survive it. Everyone who has ever had the "we lost your data" email from AWS knows at the end of the day the cloud is just someone else's data center with neat provisioning tools and services.
It's probably a dedicated government type thing where the data is housed seperately from normal AWS
“It’s not the cloud. It’s just someone else’s computer.” - MM
The devil is always in the details. Somehow I feel that when we offload the responsibility to some one else we get this feeling that the other person/entity would be doing full diligence and whatever else is required to carry out the job perfectly. However in reality most of the times they just do the bare minimum to pass your evaluation criteria to get the job.