we have been using Ola's Maintenance Solution and Database backup direct to URL since we migrated our system to Azure IAAS. We have multi terabyte DB's (approx 40% Filestream data) and therefore split the backups over multiple files to keep them below 195GB each. We had no issues until the last couple of weeks where the Full backup started to fail with an IO Device Error, telling me that the file size was greater than the 195GB limit so I increased the @NumberOfFiles parameter. The first week this worked, the next week it failed again even though the DB had only grown a few GB in size. I ended up having to add 10 to the number of files parameter and the backup completed successfully.
The issue is, most files written to are approx 90GB and 4 are approx 180GB. Does anyone know the reason for the un-equal file sizes and a way to prevent this?
EXECUTE [dbo].[DatabaseBackup] @Databases = '<dbname>', @URL = '<storage account>', @BackupType = 'FULL', @Compress = 'Y', @Verify = 'Y', @CheckSum = 'Y', @LogToTable = 'Y', @MaxTransferSize = 4194304, @Blocksize = 65536, @NumberOfFiles = 36
Thanks in advance