We use some
- block blobs to store some durable resources and then
- page blobs to store event data
We need to backup the blobs, so I tried to use AzCopy. It works ok on my dev machine, but it fails on other slow machine with error "The remote server returned an error: (412) The condition specified using HTTP conditional header(s) is not met.." almost every time.
We write to page blobs quite often (might be up to several times in a second, but this is not so common case), so this might be the reason.
Is there any better strategy how to backup the changing blobs? Or is there any way how to bypass the problem with ETag used by AzCopy?
A changed ETag will always halt a copy, since a changing ETag signifies that the source has changed.
The general approach to blob backup is subjective, but objectively:
- blob copies within Azure itself, in the same region, from Storage account to Storage account, are going to be significantly faster than trying to copy a blob to an on-premises location (due to general Internet latency) or even copying from storage account to local disk on a VM.
- Blobs support snapshots (which take place relatively instantly). If you create a snapshot, the snapshot remains unchanged, allowing you to then execute a copy operation against the snapshot instead of the actual blob itself (using AzCopy in your case) without fear of the source data changing during the copy. Note: You can create as many snapshots as you want; just be careful, since storage size grows as the underlying original blob changes.