Comments (6)
Just rewrite the still valid kv in a new blob file in next merge. So level_merge would increase write amplification.
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yes,i know.but I still have 2 questions
1.But if I don’t set a gc tag to this vtable, it still involve in a merge if it Has compaction related keys.
2.only valid compaction related keys can be rewritten,if some keys never involves in a compaction,the vtable still contains valid values even though the portion is small,and we cant delete the vtable. how can we solve the problem,this may cause huge space amplification
from titan.
yes,i know.but I still have 2 questions 1.But if I don’t set a gc tag to this vtable, it still involve in a merge if it Has compaction related keys. 2.only valid compaction related keys can be rewritten,if some keys never involves in a compaction,the vtable still contains valid values even though the portion is small,and we cant delete the vtable. how can we solve the problem,this may cause huge space amplification
vtable means blobfile here
from titan.
- Yes, check
ShouldMerge
- That's true. We have observed it in tests. It has huge space amplification for update intensive workload. That's why it's not GA.
from titan.
- Yes, check
ShouldMerge
- That's true. We have observed it in tests. It has huge space amplification for update intensive workload. That's why it's not GA.
thanks,but i noticed that when I open db, a regular gc Thread will be initialized (it will quit and never call again if no file needs go).even we enable level Merge, I found that when I
reopen a db,this regular gc thread will be initialized and clean some blob files which meet threshold. But if open a new db(level merge enable),this thread will be initialized and quit quickly,cant do regular gc in the future unless i reopen the db
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Level merge is a alternative to regular gc, so need to call background gc if level merge enabled
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Related Issues (20)
- When is it compatible with RocksDB 7.5.3? HOT 1
- blob file_level_ in blobfilemeta HOT 1
- db_bench core HOT 3
- io_read && io_write HOT 1
- parameter file_size is always 0 HOT 1
- Question about `TitanDBImpl::GetOldestSnapshotSequence()` HOT 2
- bug: key in compaction filter is internal key instead of userkey after apply IsStackedBlobDbInternalCompactionFilter HOT 9
- Any compact mechanism on titan's manifest file ? HOT 1
- Lazy load value in iterator HOT 1
- Blob file is left untouched in fallback mode HOT 3
- Store BlobStorage pointer in ColumnFamilyHandle
- Why titan forcibly set total_order_seek to true ? HOT 5
- File Size Not Really Used in GC HOT 1
- Leverage file system hole punching to avoid GC rewrite
- LRU cache misuse for BlobFileCache causes significant performance degradation HOT 3
- Whether titan can use the rocksdb original version or not HOT 1
- mirror the RocksDB's async IO optimization to titan in scan
- Wrong config when use DB::open without cf configs HOT 2
- BlobIndex will be broken and failed to decode when zero-terminated in blob handle in compaction filter HOT 2
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