**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 :)

{
    String partition_id;
    if (moving_part)
        partition_id = partition->as<ASTLiteral &>().value.safeGet<String>();
    else
        partition_id = getPartitionIDFromQuery(partition, local_context);
    DataPartsVector parts;
    if (moving_part)
    {
        auto part_info = MergeTreePartInfo::fromPartName(partition_id, format_version);
        parts.emplace_back(getActiveContainingPart(part_info));
        if (!parts.back() || parts.back()->name != part_info.getPartName())
            throw Exception("Part " + partition_id + " is not exists or not active", ErrorCodes::NO_SUCH_DATA_PART);
    }
    else
        parts = getVisibleDataPartsVectorInPartition(local_context, partition_id);
    auto volume = getStoragePolicy()->getVolumeByName(name);
    if (!volume)
        throw Exception("Volume " + name + " does not exists on policy " + getStoragePolicy()->getName(), ErrorCodes::UNKNOWN_DISK);
    if (parts.empty())
        throw Exception("Nothing to move (сheck that the partition exists).", ErrorCodes::NO_SUCH_DATA_PART);
    std::erase_if(parts, [&](auto part_ptr)
        {
            for (const auto & disk : volume->getDisks())
            {
                if (part_ptr->data_part_storage->getDiskName() == disk->getName())
                {
                    return true;