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I have a Windows Server 2012 R2 EC2 instance on AWS platform, with 2 EBS volume attached, the first (C:) for Windows SO (root volume) and the second (D:) for static file storage served by http server.

During the day, some file are read and write on D:\ but during the night the files are only read (no create/update files).

If during the night (in read only context) i make a EBS snapshot of D:\ without reboot (for backup purpose), the snapshot is safe/consistent?

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Are you actually re-mounting the filesystem as read-only? If so, then yes, the filesystem will be in a consistent state.

If, though, by "read only" you mean that there are few (or no) writes, there are still no guarantees that the filesystem will be in a consistent state. It's likely that it will work, though, but as I said, no guarantees.

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    it's the second choise, and i'm sure there aren't write operation. What happens if the snapshot isn't consistent? Can i re-mount it? – Simone Nigro Dec 19 '15 at 16:01
  • a inconsistent snapshot can be remounted? – Simone Nigro Dec 19 '15 at 16:46
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    Since the filesystem will be in an inconsistent state, the OS will want to do a filesystem check before mounting. This will identify filesystem issues, but unless your filesystem is truly unmounted cleanly before the snapshot, file corruption can never be 100% ruled out. – EEAA Dec 19 '15 at 16:51
  • sorry, i have another question (the last one) :D Do you know how long is downtime of ec2 instance for create a snapshot? – Simone Nigro Dec 19 '15 at 17:13
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    It depends on too many factors for me to give you good information about that. Test it on your setup and find out. – EEAA Dec 19 '15 at 17:29

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