**Describe the bug**

Since we upgraded to 20.10.3.30, one of our clickhouse cluster takes much more time to start. (Up to 50 minutes, and before it took ~3 minutes)
The log file is filled with
>  <Debug> DiskLocal: Reserving 1.00 MiB on disk `default`, having unreserved 16.90 TiB

Additionally, the memory consumption increases, linearly, a lot (up to arround 230 G for us) and then drop back to normal values once clickhouse finished starting up. During that loading phase, a single CPU core is used at 100%.
If that memory is not available for the machine, clickhouse gets OOMed by the kernel.


**How to reproduce**
* Issue appeared after we upgraded to ClickHouse server version 20.10.3.30

* How could I find wich of our tables may be responsible for that ?


**Expected behavior**
A fast startup :)

bool supportsLightweightDelete() const override;
    NamesAndTypesList getVirtuals() const override;
    bool mayBenefitFromIndexForIn(const ASTPtr & left_in_operand, ContextPtr, const StorageMetadataPtr & metadata_snapshot) const override;
    
    
    struct SnapshotData : public StorageSnapshot::Data
    {
        DataPartsVector parts;
    };
    StorageSnapshotPtr getStorageSnapshot(const StorageMetadataPtr & metadata_snapshot, ContextPtr query_context) const override;
    
    void loadDataParts(bool skip_sanity_checks);
    String getLogName() const { return *std::atomic_load(&log_name); }
    Int64 getMaxBlockNumber() const;
    struct ProjectionPartsVector
    {
        DataPartsVector projection_parts;
        DataPartsVector data_parts;
    };
    
    DataParts getDataParts(const DataPartStates & affordable_states) const;
    DataPartsVector getDataPartsVectorForInternalUsage(
        const DataPartStates & affordable_states, const DataPartsLock & lock, DataPartStateVector * out_states = nullptr) const;
    
    
    DataPartsVector getDataPartsVectorForInternalUsage(
        const DataPartStates & affordable_states, DataPartStateVector * out_states = nullptr) const;
    
    ProjectionPartsVector getProjectionPartsVectorForInternalUsage(
        const DataPartStates & affordable_states, DataPartStateVector * out_states = nullptr) const;