# Paralel Initial Block Download PIBD TESTING **URL:** \ **Category:** Development and Technical Discussion\ **Created:** [June 15, 2023, 12:37pm UTC](https://forum.grin.mw/t/paralel-initial-block-download-pibd-testing/10587 "2023-06-15T12:37:17Z")\ **Posts on this page:** 8\ **Page:** 3
**Author:** ![noobvie](https://avatars.discourse-cdn.com/v4/letter/n/9d8465/32.png) [@noobvie](https://forum.grin.mw/u/noobvie)\ **Post date:** [October 18, 2023, 10:57pm UTC](https://forum.grin.mw/t/paralel-initial-block-download-pibd-testing/10587/41 "2023-10-18T22:57:04Z")
Re-syncing an old node (beta3) and always stuck at PIBD 100%, not sure why. ---
**Author:** ![ardocrat](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.grin.mw/ardocrat/32/5164_2.png) [@ardocrat](https://forum.grin.mw/u/ardocrat)\ **Post date:** [October 19, 2023, 7:58am UTC](https://forum.grin.mw/t/paralel-initial-block-download-pibd-testing/10587/42 "2023-10-19T07:58:00Z")
We definitely found a bug here, old node is losing MMR root after PIBD sync for some reason. I submitted PR to prevent stuck [Handle invalid MMR root to prevent sync thread panic by ardocrat · Pull Request #3774 · mimblewimble/grin · GitHub](https://github.com/mimblewimble/grin/pull/3774), but it not fixes problem at all, just should start non-PIBD sync. ---
**Author:** ![Anynomous](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.grin.mw/anynomous/32/2928_2.png) [@Anynomous](https://forum.grin.mw/u/Anynomous)\ **Post date:** [October 19, 2023, 11:52am UTC](https://forum.grin.mw/t/paralel-initial-block-download-pibd-testing/10587/43 "2023-10-19T11:52:16Z")
I started my node after 2 months of downtime. The node synced the missing blocks without encountering any issues. Also did a clean sync, deleting all blockchain data. Again synced without issues. _[grin-v5.2.0-beta.2-win-x64 on Windows Pro]_ ---
**Author:** ![ardocrat](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.grin.mw/ardocrat/32/5164_2.png) [@ardocrat](https://forum.grin.mw/u/ardocrat)\ **Post date:** [October 19, 2023, 7:48pm UTC](https://forum.grin.mw/t/paralel-initial-block-download-pibd-testing/10587/44 "2023-10-19T19:48:50Z")
Caught same error on 5 months old chain data, when it was no even PIBD @ _grin-v5.2.0-beta.3, Linux_ with this fix [Handle invalid MMR root to prevent sync thread panic by ardocrat · Pull Request #3774 · mimblewimble/grin · GitHub](https://github.com/mimblewimble/grin/pull/3774), now its just restarting PIBD sync over and over again. I am going to share my chain data at cloud, so everyone can try to reproduce. At logs I can see: ![image](https://canada1.discourse-cdn.com/flex036/uploads/grin/original/2X/b/b1ab78f8ae3711238e40f3a6c59a9bf5ef530caf.png) And after all warnings: ```auto 20231019 22:56:13.798 ERROR grin_servers::grin::sync::state_sync - pibd_sync restart: chain reset error = Store Error: NotFoundErr("Block with hash: 00001d5480ef"), reason: DB Not Found Error: Block with hash: 00001d5480ef ``` **Link to chain data from non-PIBD node (15.05.2023)**: > **[chain\_data.zip](https://drive.google.com/file/d/1Lg2SPPQOjc9FprMs5caV1IZU6qlSNqha/edit)** > > Google Drive file. **Update** : state here was not finalized, so last error is reasonable as PIBD started sync here from 95% after updating all headers at 1st step. ---
**Author:** ![ardocrat](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.grin.mw/ardocrat/32/5164_2.png) [@ardocrat](https://forum.grin.mw/u/ardocrat)\ **Post date:** [October 19, 2023, 9:23pm UTC](https://forum.grin.mw/t/paralel-initial-block-download-pibd-testing/10587/45 "2023-10-19T21:23:33Z")
**Link chain data from PIBD node (18.08.2023):** > **[chain\_data\_pibd.zip](https://drive.google.com/file/d/1QngeAd5nAlGkNRu4aneLix_4MMQaCvwG/view?usp=share_link)** > > Google Drive file. PIBD started sync here from 35% after updaing all headers at 1st step. ---
**Author:** ![noobvie](https://avatars.discourse-cdn.com/v4/letter/n/9d8465/32.png) [@noobvie](https://forum.grin.mw/u/noobvie)\ **Post date:** [October 19, 2023, 10:13pm UTC](https://forum.grin.mw/t/paralel-initial-block-download-pibd-testing/10587/46 "2023-10-19T22:13:48Z")
> [@ardocrat](#): > > non-PIBD sync. is it possible to start full sync without PIBD step? ---
**Author:** ![oryhp](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.grin.mw/oryhp/32/2923_2.png) [@oryhp](https://forum.grin.mw/u/oryhp)\ **Post date:** [October 20, 2023, 10:09am UTC](https://forum.grin.mw/t/paralel-initial-block-download-pibd-testing/10587/47 "2023-10-20T10:09:47Z")
Many thanks for actively testing and debugging! I’m not sure the warnings are related to the error you got. By looking at it quickly, we can rewind multiple blocks at this loop [https://github.com/mimblewimble/grin/blob/master/chain/src/txhashset/txhashset.rs#L1611](https://github.com/mimblewimble/grin/blob/master/chain/src/txhashset/txhashset.rs#L1611) Each rewind updates the `output_pos` db entries by removing them from the block. The `output_pos` is not per block, but a global state. So if block 10 creates output O1 and then block 20 spends it, O1 will be thrown out from `output_pos`. Now if we rewind before block 10, we’ll iterate over each block to remove the outputs that were created, but O1 no longer exists because it was spent. My theory is that this is why you see these warnings. It’s strange though that we’d have such large reorgs. Perhaps people spend their outputs right away in the next block? It’d be good to know the length of reorgs and see how outputs were spent to confirm this, but I’m not sure that’s actually an error hence the WARN logs. The error is definitely strange… we keep quite a few blocks around for a rewind iirc. ---
**Author:** ![ardocrat](https://yyz2.discourse-cdn.com/flex036/user_avatar/forum.grin.mw/ardocrat/32/5164_2.png) [@ardocrat](https://forum.grin.mw/u/ardocrat)\ **Post date:** [October 20, 2023, 1:37pm UTC](https://forum.grin.mw/t/paralel-initial-block-download-pibd-testing/10587/48 "2023-10-20T13:37:42Z")
> [@noobvie](#): > > without PIBD step Only in some cases: - If there is no-PIBD peers For me it started after applying this fix ([Handle invalid MMR root to prevent sync thread panic by ardocrat · Pull Request #3774 · mimblewimble/grin · GitHub](https://github.com/mimblewimble/grin/pull/3774)) on this 2-months old state [chain\_data\_pibd.zip - Google Drive](https://drive.google.com/file/d/1QngeAd5nAlGkNRu4aneLix_4MMQaCvwG/view?usp=share_link) when root could not be calculated and I got message ` No PIBD-enabled max-difficulty peers for the past 60 seconds`. Some records from logs: ```auto 20231020 02:46:23.586 DEBUG grin_chain::txhashset::txhashset - Error returned, discarding txhashset extension: Store Error: NotFoundErr("Block with hash: 0000d50d51d0"), reason: DB Not Found Error: Block with hash: 0000d50d51d0 20231020 02:46:23.586 ERROR grin_servers::grin::sync::state_sync - pibd_sync restart: chain reset error = Store Error: NotFoundErr("Block with hash: 0000d50d51d0"), reason: DB Not Found Error: Block with hash: 0000d50d51d0 20231020 02:46:32.545 DEBUG grin_chain::txhashset::txhashset - Rewind header extension to 0003f168a190 at 2494941 from 0003f168a190 at 2494941 ... 20231020 02:47:27.332 INFO grin_servers::grin::sync::state_sync - No PIBD-enabled max-difficulty peers for the past 60 seconds - Aborting PIBD and falling back to TxHashset.zip download 20231020 02:47:27.342 ERROR grin_servers::grin::sync::state_sync - state_sync: error = Aborting PIBD error. restart fast sync 20231020 02:47:27.346 DEBUG grin_servers::grin::sync::state_sync - state_sync: before txhashset request, header head: 2494943 / 000328fb421f, txhashset_head: 2491920 / 00034b16ee06 20231020 02:47:27.346 DEBUG grin_p2p::peer - Asking 142.132.167.15:3414 for txhashset archive at 2491920 00034b16ee06. 20231020 02:47:27.346 DEBUG grin_chain::types - sync_state: sync_status: TxHashsetPibd { aborted: true, errored: true, completed_leaves: 0, leaves_required: 18709626, completed_to_height: 1, required_height: 2491920 } -> TxHashsetDownload(TxHashsetDownloadStats { start_time: 2023-10-19T23:47:27.346560354Z, prev_update_time: 2023-10-19T23:47:27.346560431Z, update_time: 2023-10-19T23:47:27.346560396Z, prev_downloaded_size: 0, downloaded_size: 0, total_size: 0 }) ``` [Previous page](https://forum.grin.mw/t/paralel-initial-block-download-pibd-testing/10587.md?page=2)