**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 :)

{
            Ordinary            = 0,    
            Collapsing          = 1,
            Summing             = 2,
            Aggregating         = 3,
            Replacing           = 5,
            Graphite            = 6,
            VersionedCollapsing = 7,
        };
        Mode mode;
        
        String sign_column;
        
        Names columns_to_sum;
        
        String version_column;
        
        Graphite::Params graphite_params;
        
        void check(const StorageInMemoryMetadata & metadata) const;
        String getModeName() const;
    };