I've heard that NTFS supports having multiple datastreams in a single file. Where you can specify a stream to read or write from other than the main one.
I see quite a bit of potential here, for different reasons.
Is there a filesystem for linux that achieves the same? Have attempts been made at making one? Why or why not would one be a good idea? What would it take for a filesystem to have this kind of feature?
Files in NTFS only have a single main data stream, but they can have additional ones called Alternate data stream (ADS). ADS was introduced for classic Mac interoperability because Apple used resource forks to store additional data which is a kind of data fork
ADS has limited use and was mainly abused by viruses and malware. Besides, using forks makes it prone to data loss when copying using normal tools or copying to a non-supported file system. Therefore *nix didn't quite catch up on that. Even MS tried to use it for thumbnails in Windows 2000 but then abandoned the idea in XP. And when they introduced ReFS (which is the successor to NTFS) initially they dropped ADS support completely
The only common valid use of ADS nowadays is to store zone information to indicate where the file was downloaded from, in order to protect users from attacks from the internet. This needs little space so it was gaining popularity in other platforms. In the *nix world extended file attributes, which is additional data but with limited size, was starting to be added to most *nix file systems during the booming of the internet era in the 2000s. For example FreeBSD started supporting extended attributes since version 5.x in 2003
In Linux, the ext2, ext3, ext4, JFS, Squashfs, UBIFS, Yaffs2, ReiserFS, Reiser4, XFS, Btrfs, OrangeFS, Lustre, OCFS2 1.6, ZFS, and F2FS filesystems support extended attributes (abbreviated xattr) when enabled in the kernel configuration. Any regular file or directory may have extended attributes consisting of a name and associated data. The name must be a null-terminated string prefixed by a namespace identifier and a dot character. Currently, four namespaces exist: user, trusted, security and system. The user namespace has no restrictions with regard to naming or contents. The system namespace is primarily used by the kernel for access control lists. The security namespace is used by SELinux, for example.
Support for the extended attribute concept from a POSIX.1e draft[citation needed] that had been withdrawn in 1997 was added to Linux around 2002. As of 2016, they are not yet in widespread use by user-space Linux programs, but are used by Beagle, OpenStack Swift, Dropbox, KDE's semantic metadata framework (Baloo), Chromium, Wget and cURL.
The Linux kernel allows extended attribute to have names of up to 255 bytes and values of up to 64 KiB, as do XFS and ReiserFS, but ext2/3/4 and btrfs impose much smaller limits, requiring all the attributes (names and values) of one file to fit in one "filesystem block" (usually 4 KiB). Per POSIX.1e,[citation needed] the names are required to start with one of security, system, trusted, and user plus a period. This defines the four namespaces of extended attributes.
https://en.wikipedia.org/wiki/Extended_file_attributes#Linux
As noted previously, ReFS originally didn't support ADS but ADS with limited length was added back to newer ReFS versions but which makes it essentially extended attributes
Solaris 9 in 2002 is the first Unix to have forks, therefore Solaris' ZFS is probably the only Unix file system with forks, although confusingly they call it "extended attributes"
