**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 :)

start_with_valid_prefix = true;
                    break;
                }
            }
            if (!start_with_valid_prefix)
                continue;
            const std::string & full_path = fullPath(disk, it->path());
            try
            {
                if (disk->isDirectory(it->path()) && isOldPartDirectory(disk, it->path(), deadline))
                {
                    if (temporary_parts.contains(basename))
                    {
                        LOG_WARNING(log, "{} is in use (by merge/mutation/INSERT) (consider increasing temporary_directories_lifetime setting)", full_path);
                        continue;
                    }
                    else
                    {
                        LOG_WARNING(log, "Removing temporary directory {}", full_path);
                        
                        
                        
                        
                        
                        bool keep_shared = false;
                        if (it->path().find("fetch") != std::string::npos)
                        {
                            keep_shared = disk->supportZeroCopyReplication() && settings->allow_remote_fs_zero_copy_replication;
                            if (keep_shared)
                                LOG_WARNING(log, "Since zero-copy replication is enabled we are not going to remove blobs from shared storage for {}", full_path);