Managing your files

There's some specific info you should know before you get your first file on Sia.

As with any file storage or backup solution, Sia should not be your sole location for critical files.

Uploading

Uploading happens in Sia-UI or your preferred command-line interface. Sia-UI has your standard file browser or drag-and-drop options, just like any other file storage application. There are special commands that you'll want to become familiar with when using the CLI version of Sia, which is called siac.

When you begin to upload a file to Sia, it has to get processed on your machine to allow for maximum redundancy and security on the network. It is first split into manageable chunks. Each chunk is then run through a process that creates 30 pieces, each of which gets encrypted before being sent to a different host. Only 10 of the 30 pieces are needed to reconstruct a chunk, but no host ever sees more than one. This means, for each part of your original file, 20 hosts could drop from the network and your data will still be safe and secure.

For the more technical readers, here is what happens behind the scenes:

• Files are chunked into 40MB chunks (if a file is smaller, it is padded to 40MB so that data looks identical as it moves across networks)

• Each chunk is then erasure-coded using Reed-Solomon encoding. After processing, each chunk has 30 unique 4MB pieces associated with it.

• Each piece is then encrypted using Threefish and uploaded to a distinct host.

• Because Reed-Solomon encoding is done with 10 data shards and 20 parity shards, any 10 pieces are sufficient for rebuilding the file.

That's a lot of details but just know: you don't have to do anything, or even see that this process happens.

Limits on uploading*

*These numbers will change over time.

Maximum total storage: Sia can currently handle 35 TB of data in a single node, or installation of Sia.

File size: The minimum file size on Sia is currently 40 MB. Uploading smaller files isn't a problem, but Sia will pad each of them out to 40 MB. Your 80 MB short video stays 80 MB. But your 8 MB photo and your 100 KB document each become 40 MB when uploaded.

This means that, if you're uploading many small files, you'll save a lot of money by zipping them up together before uploading. This minimum file size will be significantly reduced in a future update.

Health and Redundancy

In Sia, you'll see the health of your files represented as a percentage. This refers to how many pieces of this file are available. You always want this to be 100%, which means that all 30 pieces of your file are stored on hosts. Sia is smart though – if a host goes offline, it will re-duplicate that piece on a new host the next time it checks.

Sia can only check when it's active though, so be sure to open Sia periodically to refresh the health of your files.

Downloading

Downloading files happens right through the app as well. There's a small download icon next to each file in your list. Downloading requires Siacoins since you pay for the bandwidth you use.

Maintaining Data **

In order to make sure that your data is always available, there's a couple of important tasks you should periodically perform.

• Refreshing your allowance - About six weeks after your contracts are created, your allowance attempts to refill itself. Sia will never spend more than your allowance, so it needs to be refilled to facilitate contract renewals and downloads through the rest of the contract period. ! The allowance will refill automatically when you open Sia.

• Renewing your contracts - Your storage contracts will renew automatically at the end of the contract period. By default, Sia will attempt to renew your contract within about 1 month of the contract expiration date. If you started renting at the beginning of January, your 3-month contracts would expire around the end of March. Sia would attempt to renew them around the beginning of March. ! Your contracts renew automatically when you open Sia.

• Boosting file health - File health and redundancy are also boosted if needed, as described above.

Sia needs to be running with your wallet unlocked for these things to occur, so as a renter, it's a good idea to open Sia at least once a month and let it run overnight to take care of miscellaneous housekeeping tasks such as these. If you simply upload files and then never open Sia again, your allowance and your contracts will eventually expire and your files will be immediately deleted once your contracts are no longer valid.