Maybe you do not need a translation.
Different usages of the language develop its own private vocabulary (it affects from research, IT and medicine to plumbers and administrative work). In IT in particular, there are lots of loan words from English.
If spanish speaking people in your field widely know and use the term
blob, it is better to use it than to try to translate ("un calco") with a mainstream spanish word that does not have the technical meaning that you want.
For example, I would not tell one of my fellow programmers that "esta función devuelve una cadena (o una corriente, o un arreglo)"; I would tell them that "esta función devuelve un String (o un Stream, o un array)". They are more likely to understand me if I use the latter way. Otherwise, when I am out of the technical language, speaking of everyday events, I would tell them that "ayer tropecé con una cadena" y no que "ayer tropecé con un string".
In essence, the fact that a mainstream word from English can be translated in a mainstream word from Spanish does not mean that you ought to (or should) do the translation when using the same word in a technical concept (think of words like "robot" -which means work in hungarian-).