With S3 Browser you can reliably upload and download your files to and from Amazon S3. S3 Browser supports the number of features allowing you to be sure that data is not corrupted traversing the network.
Data Integrity checking when uploading files
To enable data integrity checking when uploading files, please open Tools, Options, Data IntegrityClick Tools, Options, Data Integrity
When this option is turned on, S3 Browser calculates an MD5 hash for an each file you upload and sends this hash to Amazon S3. Amazon S3 calculates the hash on the server side and compares it with the hash provided by S3 Browser. If they do not match, returns an error. The file will not be written on Amazon S3 if hashes do not match.
This option is also strongly recommended if you would like to test data integrity when downloading files (see below).
Data Integrity checking when downloading files
To enable data integrity checking when downloading files, please open Tools, Options, Data IntegrityClick Tools, Options, Data Integrity
If this option is turned on, S3 Browser calculates the hash for downloaded file and compares it with the hash returned by the server (Amazon S3). If hashes do not match it returns the error and file is not written on local disk.
There are two modes of data integrity checking for downloaded files:
In Flexible mode S3 Browser performs data integrity test only for files for which valid md5 hash is provided by the server. Files with invalid hashes are not checked and treated as valid.
In Strict mode S3 Browser checks all files. Files with invalid hashes are treated as corrupted.
The reason for two modes of data integrity checking
Amazon S3 doesn’t provide an MD5 hash for files uploaded using multipart upload feature. Thereby there is no way to get the hash to compare with.
Amazon S3 compatible storages may also use another hashing algorithm and format for storing file hashes or not provide file hashes at all.
You can choose how to handle the files for which no hash is provided.
How to avoid the ‘missing hash’ issue
First, you can enable data integrity checking when uploading files. When this option is turned on, S3 Browser writes the hash in file metadata during uploading (Amazon S3 allows you to store any custom information for an each file).
Later, when you download this file, S3 Browser can extract saved hash from the metadata and compare it with calculated value.
Another way is to disable multipart uploads in Tools, Options, General, but this could reduce the speed of your uploads. Plus you can upload files up to the 5Gb in size only, for larger files you need to enable multipart uploads.
How to fix the hashes for already uploaded files
The method described below allows you to fix file hashes for files up to the 5Gb in size. There is no way to fix hashes for files over 5Gb in size, you can only re-upload them with data integrity checking for uploads enabled or select the Flexible mode for data integrity checking for downloads.
To fix file hashes for files up to the 5Gb in size:
- Start S3 Browser and choose the bucket
- Select one or multiple files
- Open the Http Headers tab and click Apply
S3 Browser will update the ETag header containing MD5 hash using simple COPY request.
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