Hi Kamal and Haiying Cai: maybe you notice that my kafka clusters set 1day local + 3 days-7 days remote. thus Haiying Cai‘s configure is 3 hours local + 3 days remote.
I can explain more about my configure. I try to avoid the latency for some delay consumer to access the remote. Maybe some applications may encounter some unexpected issue. but we need to give enough time to handle it. In the period, we don't want the consumer to access the remote to hurt the whole kafka clusters. So one day is our expectation. I saw one statement in Haiying Cai KIP1248: " Currently, when a new consumer or a fallen-off consumer requires fetching messages from a while ago, and those messages are no longer present in the Kafka broker's local storage, the broker must download the message from the remote tiered storage and subsequently transfer the data back to the consumer. " Extend the local retention time is how we try to avoid the issue (Here, we don't consider the case one new consumer use the earliest strategy to consume. it is not often happen in our cases.) So. based my configure. I will see there is one day's duplicated segment wasting in remote storage. Thus I don't use them for real time analyst or care about the fast reboot or some thing else. So propose this KIP to take one topic level optional feature to help us to reduce waste and save money. Regards Jian jian fu <[email protected]> 于2025年12月2日周二 18:42写道： > Hi Kamal: > > Thanks for joining this discussion. Let me try to classify my understands > for your good questions: > > 1 Kamal : Do you also have to update the RemoteCopy lag segments and > bytes metric? > Jian: The code just delay the upload time for local segment. So it > seems there is no need to change any lag segments or metrics. right? > > 2 Kamal : As Haiying mentioned, the segments get eventually uploaded to > remote so not sure about the > benefit of this proposal. And, remote storage cost is considered as low > when compared to broker local-disk. > Jian: The cost benefit is about the total size for occupied. Take AWS > S3 as example. Tiered price for: 1 GB is 0.02 USD (You can refer to > https://calculator.aws/#/createCalculator/S3). > It is cheaper than local disk. So as I mentioned that the saving money > depend on the ratio local vs remote retention time. If your set the remote > storage time as a long time. The benefit is few, It is just avoiding the > waste instead of cost saving. > So I take it as topic level optional configure instead of default > feature. > > 3 Kamal: It provides some cushion during third-party object storage > downtime. > Jian: I draw one picture to try to under the logic( > https://github.com/apache/kafka/pull/20913#issuecomment-3601274230). You > can help to check if my understanding is right. I seemed that no difference > for them. So for this question. maybe we need to discuss more about it. The > only difference maybe we may increase a little local disk for temp due to > the delay for upload remote. So in the original proposal. I want to upload > N-1 segments. But it seems the value is not much. > > BTW. I want to classify one basic rule: this feature isn't to change the > default behavior. and the saving amount is not very big value in all cases. > It is suitable for part of topic which set a low ratio for remote/local > such as 7days/1days or 3days/1day > At the last. Thanks again for your time and your comments. All the > questions are valid and good for us to thing more about it. > > Regards > Jian > > > Kamal Chandraprakash <[email protected]> 于2025年12月2日周二 > 17:41写道： > >> 1. Do you also have to update the RemoteCopy lag segments and bytes >> metric? >> 2. As Haiying mentioned, the segments get eventually uploaded to remote so >> not sure about the >> benefit of this proposal. And, remote storage cost is considered as low >> when compared to broker local-disk. >> It provides some cushion during third-party object storage downtime. >> >> >> On Tue, Dec 2, 2025 at 2:45 PM Kamal Chandraprakash < >> [email protected]> wrote: >> >> > Hi Jian, >> > >> > Thanks for the KIP! >> > >> > When remote storage is unavailable for a few hrs, then with lazy upload >> > there is a risk of the broker disk getting full soon. >> > The Admin has to configure the local retention configs properly. With >> > eager upload, the disk utilization won't grow >> > until the local retention time (expectation is that all the >> > passive segments are uploaded). And, provides some time >> > for the Admin to take any action based on the situation. >> > >> > -- >> > Kamal >> > >> > On Tue, Dec 2, 2025 at 10:28 AM Haiying Cai via dev < >> [email protected]> >> > wrote: >> > >> >> Jian, >> >> >> >> Understands this is an optional feature and the cost saving depends on >> >> the ratio between local.retention.ms and total retention.ms. >> >> >> >> In our setup, we have local.retention set to 3 hours and total >> retention >> >> set to 3 days, so the saving is not going to be significant. >> >> >> >> On 2025/12/01 05:33:11 jian fu wrote: >> >> > 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 >> >> > > > >> >> > >> > >> > >> > > > >
