> A datastore implementation using sharded directories and flat files to store data
`go-ds-flatfs` is used by `go-ipfs` to store raw block contents on disk. It supports several sharding functions (prefix, suffix, next-to-last/*).
## Table of Contents
-[Install](#install)
-[Usage](#usage)
-[Contribute](#contribute)
-[License](#license)
## Install
`go-ds-flatfs` can be used like any Go module:
```
import "github.com/ipfs/go-ds-flatfs"
```
`go-ds-flatfs` uses [`Gx`](https://github.com/whyrusleeping/gx) and [`Gx-go`](https://github.com/whyrusleeping/gx-go) to handle dependendencies. Run `make deps` to download and rewrite the imports to their fixed dependencies.
## Usage
Check the [GoDoc module documentation](https://godoc.org/github.com/ipfs/go-ds-flatfs) for an overview of this module's
functionality.
### DiskUsage and accuracy
This datastore implements the [`PersistentDatastore`](https://godoc.org/github.com/ipfs/go-datastore#PersistentDatastore) interface. It offers a `DiskUsage()` method which strives to find a balance between accuracy and performance. This implies:
* The total disk usage of a datastore is calculated when opening the datastore
* The current disk usage is cached frequently in a file in the datastore root (`diskUsage.cache` by default). This file is also
written when the datastore is closed.
* If this file is not present when the datastore is opened:
* The disk usage will be calculated by walking the datastore's directory tree and estimating the size of each folder.
* This may be a very slow operation for huge datastores or datastores with slow disks
* The operation is time-limited (5 minutes by default).
* Upon timeout, the remaining folders will be assumed to have the average of the previously processed ones.
* After opening, the disk usage is updated in every write/delete operation.
This means that for certain datastores (huge ones, those with very slow disks or special content), the values reported by
`DiskUsage()` might be reduced accuracy and the first startup (without a `diskUsage.cache` file present), might be slow.
If you need increased accuracy or a fast start from the first time, you can replace the `diskUsage.cache` file (while the
datastore is not open), with the right disk usage value in size. I.e., in the datastore root:
$ du -sb .
3919232394 .
$ echo -n "3919232394" > diskUsage.cache
## Contribute
PRs accepted.
Small note: If editing the README, please conform to the [standard-readme](https://github.com/RichardLitt/standard-readme) specification.
