Improving storage efficiency in Magic Pocket, Dropbox's immutable blob store

> Last year, we rolled out a new service that changed how data is placed across Magic Pocket. The change reduced write amplification for background writes, so each write triggered fewer backend storage operations. But it also had an unintended side effect: fragmentation increased, pushing storage overhead higher. Most of that growth came from a small number of severely under-filled volumes that consumed a disproportionate share of raw capacity

Me thinking big corps with huge infrastructure bills meticulously model changes like that using the production data they have, so that exact change in all the metrics they care about is known upfront. Turned out they are like me: deploy and see what breaks.

Re: Improving storage efficiency in Magic Pocket, Dropbox's immutable blob store

#7

Post by hs86 » Thu, Apr 09, 2026, 2:01 PM UTC

Google recently increased storage from 2 TB to 5 TB on their $20 AI plan, while Dropbox is still stuck at 2 or 3 TB for their $12/$20 plans.

They moved from 1 TB to 2 TB in mid-2019, and I wonder if they ever plan to pass on any of the gains from the past seven years of technological advancements, or if those gains are simply being captured on their side while we keep paying the same.

Re: Improving storage efficiency in Magic Pocket, Dropbox's immutable blob store

#8

Post by [deleted] » Thu, Apr 09, 2026, 2:13 PM UTC

hs86 wrote: post #7

Google recently increased storage from 2 TB to 5 TB on their $20 AI plan, while Dropbox is still stuck at 2 or 3 TB for their $12/$20 plans. They moved from 1 TB to 2 TB in mid-2019, and I wonder if they ever plan to pass on any of the gains from the past seven years of technological advancements, or if those gains are simply being captured on their side while we keep paying the same.

[deleted]

Re: Improving storage efficiency in Magic Pocket, Dropbox's immutable blob store

#9

Post by timmmmmmay » Thu, Apr 09, 2026, 2:27 PM UTC

hs86 wrote: post #7

Google recently increased storage from 2 TB to 5 TB on their $20 AI plan, while Dropbox is still stuck at 2 or 3 TB for their $12/$20 plans. They moved from 1 TB to 2 TB in mid-2019, and I wonder if they ever plan to pass on any of the gains from the past seven years of technological advancements, or if those gains are simply being captured on their side while we keep paying the same.

are these "technological advancements" in storage in the room with us right now? because I'm looking at today's price per TB and it's higher than it was in 2020

Re: Improving storage efficiency in Magic Pocket, Dropbox's immutable blob store

#10

Post by Retr0id » Thu, Apr 09, 2026, 2:33 PM UTC

jeffbee wrote: post #5

The immutability of extents is dictated by their SMR hardware, I believe.

I don't know the full picture behind their decision-making but immutability is much easier to reason about in a distributed system, in general.