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by Jiří {x2} Činčura

Azure blob error “The specified blob or block content is invalid." even with “same” block IDs

5 Jan 2014 Azure, Azure Storage, Cloud, Lessons learned, Storage & Backup

Last week I spent fair amount of time with error The specified blob or block content is invalid. while uploading to Azure blob in blocks. If you do a quick googling you’ll find a lot of resources about fact that the block IDs need to be same of length. With maybe more googling you’ll find error codes and find InvalidBlockId might seem more appropriate for this. But this is a false path. While going through first results you’ll sooner or later find quite good article.

And you’ll read (read: I read) the short version saying, at that time already known fact, that the block IDs need to be of same length. I read that couple of times, checked my code even more times and my block IDs were of same length, indeed. Only after few hours I read complete article including the “long version”. And then it kicked me. My block IDs were of same length in the current session/run of application. But as I was debugging it, I also put there bunch of blocks with “random” IDs. These were different length. Silly me. I quickly comfirmed that fetching uncommitted blocks. Bang. Deleted the whole blob and started again. And it went smoothly now.

So there are two morals from this. Always read whole blog post (if you’re here, good job 😃). And always think outside the single “run” of application you’re currently writing/debugging; the state might be there.

Profile Picture Jiří Činčura is an independent developer focusing on data and business layers, language constructs, parallelism and databases. Specifically Entity Framework, asynchronous and parallel programming, cloud and Azure. He's Microsoft Most Valuable Professional and you can read his articles, guides, tips and tricks at