I realise it is 17 years later now, but for what it is worth now in 2019, you don't have to use a copy for this, only return a new reference / object in the acquisition function that queriers the data of your hard disks. So, don't use global hashes/arrays with this function. Then, two successive calls of the acquisition function will already return two separate instances of your data and so there is no need to copy this any further.