Hi Haiying Cai, Thanks for joining the discussion for this KIP. All of your concerns are valid, and that is exactly why I introduced a topic-level configuration to make this feature optional. This means that, by default, the behavior remains unchanged. Only when users are not pursuing faster broker boot time or other optimizations — and care more about cost — would they enable this option to some topics to save resources.
Regarding cost self: the actual savings depend on the ratio between local retention and remote retention. In the KIP/PR, I provided a test example: if we configure 1 day of local retention and 2 days of remote retention, we can save about 50%. And realistically, I don't think anyone would boldly set local retention to a very small value (such as minutes) due to the latency concerns associated with remote storage. So in short, the feature will help reduce cost, and the amount saved simply depends on the ratio. Take my company's usage as real example, we configure most of the topics: 1 day of local retention and 3–7 days of remote storage (3 days for topic with log/metric usage, 7 days for topic with normal business usage). and we don't care about the boot speed and some thing else, This KIP allows us to save 1/7 to 1/3 of the total disk usage for remote storage. Anyway, this is just a topic-level optional feature which don't reject the benifit for current design. Thanks again for the discussion. I can update the KIP to better classify scenarios where this optional feature is not suitable. Currently, I only listed real-time analytics as the negative example. Welcome further discussion to help make this KIP more complete. Thanks! Regards, Jian Haiying Cai via dev <[email protected]> 于2025年12月1日周一 12:40写道： > Jian, > > Thanks for the contribution. But I feel the uploading the local segment > file to remote storage ASAP is advantageous in several scenarios: > > 1. Enable the fast bootstrapping a new broker. A new broker doesn’t have > to replicate all the data from the leader broker, it only needs to > replicate the data from the tail of the remote log segment to the tail of > the current end of the topic (LSO) since all the other data are in the > remote tiered storage and it can download them later lazily, this is what > KIP-1023 trying to solve; > 2. Although nobody has proposed a KIP to allow a consumer client to read > from the remote tiered storage directly, but this will helps the > fall-behind consumer to do catch-up reads or perform the backfill. This > path allows the consumer backfill to finish without polluting the broker’s > page cache. The earlier the data is on the remote tiered storage, the more > advantageous it is for the client. > > I think in your Proposal, you are delaying uploading the segment but the > file will still be uploaded at a later time, I guess this can saves a few > hours storage cost for that file in the remote storage, not sure whether > that is a significant cost saved (if the file needs to stay in remote > tiered storage for several days or weeks due to retention policy). > > On 2025/11/19 13:29:11 jian fu wrote: > > Hi everyone, I'd like to start a discussion on KIP-1241, the goal is to > > reduce the remote storage. KIP: > > > https://cwiki.apache.org/confluence/display/KAFKA/KIP-1241%3A+Reduce+tiered+storage+redundancy+with+delayed+upload > > > > The Draft PR: https://github.com/apache/kafka/pull/20913 Problem: > > Currently, > > Kafka's tiered storage implementation uploads all non-active local log > > segments to remote storage immediately, even when they are still within > the > > local retention period. > > This results in redundant storage of the same data in both local and > remote > > tiers. > > > > When there is no requirement for real-time analytics or immediate > > consumption based on remote storage. It has the following drawbacks: > > > > 1. Wastes storage capacity and costs: The same data is stored twice > during > > the local retention window > > 2. Provides no immediate benefit: During the local retention period, > reads > > prioritize local data, making the remote copy unnecessary > > > > > > So. this KIP is to reduce tiered storage redundancy with delayed upload. > > You can check the test result example here directly: > > https://github.com/apache/kafka/pull/20913#issuecomment-3547156286 > > Looking forward to your feedback! Best regards, Jian > >
