Mozy glitch fogs the reliability of storage clouds

Discovery by former S Central engineer raises new questions.

Imagine if your cloud storage provider experienced a technical error that caused your bandwidth bill to balloon into the thousands of dollars.

That's a scenario feared by Dan Frith, a storage and virtualisation engineer and former employee of S Central - and now an unhappy  customer of the EMC-owned Mozy online backup storage service.

For the past week, Frith has been struggling with a glitch in his Mozy account.

When his Mozy service is working correctly, the storage cloud connects to his machine once a day to check which files on his system were updated or modified and transfers only these incremental changes to the replica of his hard drive stored in Mozy's US data centre.

On November 14, Frith noted the system connect to his machine and request to start the usual daily transfer of changed files. Strangely, Mozy was requesting a data transfer of 32 Gigabytes of data - not just the incremental changes but the entire contents of Frith's hard drive.

"It sort of smells," Frith said. "I am confident I haven't lost the data - I can still restore from one week ago, from before there was a problem. But imagine if I lost [the locally-stored] data from just the last day or two - data that was essential - how would I get that back?"

Frith has since been in regular contact with Mozy's support staff for answers, posting the discussions on his blog, but the company is yet to provide a fix.

"We recently starting experiencing an usually high amount of volume of data centre traffic that prevented the Mozy client from adequately identifying files that were previously backed up," reads a note from Devin Knighton, a public relations professional at Mozy, in a response to Frith's blog. "As a result, Mozy is sending third or fourth copies of the same files to our data centres."

Broadband concerns

Frith said that he is fortunate to have negotiated a contract with his ISP under which uploads are not calculated as part of his monthly bill.

"But I have friends that use the Mozy service that have 110GB up there, and some of them do pay for uploads," he said. "Do the maths on what he would pay if this happened to them."

Frith said that he is a home user of Mozy and "perhaps could be assured of better SLA's [service level agreements] if I went out on a limb and got Mozy Pro".

But his problem has gained the attention of cloud watchers around the globe as concerns rise around the reliability of the next generation of IT services. 

"I think this technology is still very immature," Frith said. "We get given this sense of protection from a service like this. You put your data up there, but the question is whether these operators value your data as much as you do. It's just blocks and files to them."