**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 :)

const StorageMetadataPtr & metadata_snapshot,
    UInt64 expected_size,
    const IMergeTreeDataPart::TTLInfos & ttl_infos,
    time_t time_of_move,
    size_t min_volume_index,
    bool is_insert,
    DiskPtr selected_disk) const
{
    expected_size = std::max(RESERVATION_MIN_ESTIMATION_SIZE, expected_size);
    ReservationPtr reservation;
    auto move_ttl_entry = selectTTLDescriptionForTTLInfos(metadata_snapshot->getMoveTTLs(), ttl_infos.moves_ttl, time_of_move, true);
    if (move_ttl_entry)
    {
        SpacePtr destination_ptr = getDestinationForMoveTTL(*move_ttl_entry, is_insert);
        if (!destination_ptr)
        {
            if (move_ttl_entry->destination_type == DataDestinationType::VOLUME && !move_ttl_entry->if_exists)
                LOG_WARNING(
                    log,
                    "Would like to reserve space on volume '{}' by TTL rule of table '{}' but volume was not found or rule is not "
                    "applicable at the moment",
                    move_ttl_entry->destination_name,
                    *std::atomic_load(&log_name));
            else if (move_ttl_entry->destination_type == DataDestinationType::DISK && !move_ttl_entry->if_exists)
                LOG_WARNING(
                    log,
                    "Would like to reserve space on disk '{}' by TTL rule of table '{}' but disk was not found or rule is not applicable "
                    "at the moment",
                    move_ttl_entry->destination_name,