Deleting disk zeros it out?

A good question appeared on IRC tonight. If you delete a disk in the Linode control panel is the disk zeroed out before that storage it is made available for other people's disks? If not, this is a bit worrisome because there is no warning.

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I suspect that you might be safe as the disks linode presents to the end user are stored as (i think), vhd files on disk, so when when you delete a linode disk the server just deletes the vhd file.

Because a linode doesnt get raw disk access I don't think that another customer would be able to retrieve any files from your old disk.

Of course this wouldn't stop someone who had access to the host server from retrieving the deleted disk image and recovering files from it but if they had access to the host then there really isn't much you can do short of whole disk encryption (plus if they have access to the host then you have bigger worries!).

Of course this answer does make assumptions on how Linode setup Xen so I could be totally wrong about this :P

@wtogami:

If you delete a disk in the Linode control panel is the disk zeroed out before that storage it is made available for other people's disks?
Yes. However, if you cycle a few disk images you may get chunks that were previously allocated to you (and contain your data).

This has nothing to do with Xen.

-Chris

Hmm, what if you resize a disk image smaller? Does the now-unused portion get zeroed out?

@mnordhoff:

Hmm, what if you resize a disk image smaller? Does the now-unused portion get zeroed out?
That condition is not handled. When we designed the scrubber there was no efficient and practical way to accomplish this. One could argue usage patterns of ext3 volumes favor freeing unused (or never used) space in the first place when resizing, but it's not a perfect argument.

-Chris

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