From f3340ae5f4ac6c60823bf4d14e1fcdbeaaec353c Mon Sep 17 00:00:00 2001 From: Brian Picciano Date: Sat, 21 May 2022 14:07:14 -0600 Subject: Remove old code related to static, it's not needed anymore --- ...2021-04-06-evaluation-of-network-filesystems.md | 339 --------------------- 1 file changed, 339 deletions(-) delete mode 100644 static/src/_posts/2021-04-06-evaluation-of-network-filesystems.md (limited to 'static/src/_posts/2021-04-06-evaluation-of-network-filesystems.md') diff --git a/static/src/_posts/2021-04-06-evaluation-of-network-filesystems.md b/static/src/_posts/2021-04-06-evaluation-of-network-filesystems.md deleted file mode 100644 index b80eb8d..0000000 --- a/static/src/_posts/2021-04-06-evaluation-of-network-filesystems.md +++ /dev/null @@ -1,339 +0,0 @@ ---- -title: >- - Evaluation of Network Filesystems -description: >- - There can only be one. -series: nebula -tags: tech ---- - -It's been a bit since updating my progress on what I've been lately calling the -"cryptic nebula" project. When I last left off I was working on building the -[mobile nebula][mobile_nebula] using [nix][nix]. For the moment I gave up on -that dream, as flutter and nix just _really_ don't get along and I don't want to -get to distracted on problems that aren't critical to the actual goal. - -Instead I'd like to pursue the next critical component of the system, and -that's a shared filesystem. The use-case I'm ultimately trying to achieve is: - -* All hosts communicate with each other via the nebula network. -* All hosts are personal machines owned by individuals, _not_ cloud VMs. -* A handful of hosts are always-on, or at least as always-on as can be achieved - in a home environment. -* All hosts are able to read/write to a shared filesystem, which is mounted via - FUSE (or some other mechanism, though I can't imagine what) on their computer. -* Top-level directories within the shared filesystem can be restricted, so - that only a certain person (or host) can read/write to them. - -What I'm looking for is some kind of network filesystem, of which there are -_many_. This document will attempt to evaluate all relevant projects and come up -with the next steps. It may be that no project fits the bill perfectly, and that -I'm stuck either modifying an existing project to my needs or, if things are -looking really dire, starting a new project. - -The ultimate use-case here is something like a self-hosted, distributed [keybase -filesystem](https://book.keybase.io/docs/files); somewhere where individuals in -the cluster can back up their personal projects, share files with each other, -and possibly even be used as the base layer for more complex applications on -top. - -The individuals involved shouldn't have to deal with configuring their -distributed FS, either to read from it or add storage resources to it. Ideally -the FS process can be bundled together with the nebula process and run opaquely; -the user is just running their "cryptic nebula" process and everything else is -handled in the background. - -## Low Pass Filter - -There are some criteria for these projects that I'm not willing to compromise -on; these criteria will form a low pass filter which, hopefully, will narrow our -search appreciably. - -The network filesystem used by the cryptic nebula must: - -* Be able to operate over a nebula network (obviously). -* Be open-source. The license doesn't matter, as long as the code is available. -* Run on both Mac and Linux. -* Not require a third-party to function. -* Allows for a replication factor of 3. -* Supports sharding of data (ie each host need not have the entire dataset). -* Allow for mounting a FUSE filesystem in any hosts' machine to interact with - the network filesystem. -* Not run in the JVM, or any other VM which is memory-greedy. - -The last may come across as mean, but the reason for it is that I forsee the -network filesystem client running on users' personal laptops, which cannot be -assumed to have resources to spare. - -## Rubric - -Each criteria in the next set lies along a spectrum. Any project may meet one of -thses criteria fully, partially, or not at all. For each criteria I assign a -point value according to how fully a project meets the criteria, and then sum up -the points to give the project a final score. The project with the highest final -score is not necessarily the winner, but this system should at least give some -good candidates for final consideration. - -The criteria, and their associated points values, are: - -* **Hackability**: is the source-code of the project approachable? - - 0: No - - 1: Kind of, and there's not much of a community. - - 2: Kind of, but there is an active community. - - 3: Yes - -* **Documentation**: is the project well documented? - - 0: No docs. - - 1: Incomplete or out-of-date docs. - - 2: Very well documented. - -* **Transience**: how does the system handle hosts appearing or disappearing? - - 0: Requires an automated system to be built to handle adding/removing - hosts. - - 1: Gracefully handled. - -* **Priority**: is it possible to give certain hosts priority when choosing - which will host/replicate some piece of data? - - 0: No. - - 1: Yes. - -* **Caching**: will hosts reading a file have that file cached locally for the - next reading (until the file is modified)? - - 0: No. - - 1: Yes. - -* **Conflicts**: if two hosts updated the same file at the same time, how is - that handled? - - 0: The file can no longer be updated. - - 1: One update clobbers the other, or both go through in an undefined - order. - - 2: One update is disallowed. - - 3: A copy of the file containing the "losing" update is created (ie: how - dropbox does it). - - 4: Strategy can be configured on the file/directory level. - -* **Consistency**: how does the system handle a file being changed frequently? - - 0: File changes must be propagated before subsequent updates are allowed (fully consistent). - - 1: Files are snapshotted at some large-ish interval (eventually consistent). - - 2: File state (ie content hash, last modifid, etc) is propagated - frequently but contents are only fully propagated once the file has - "settled" (eventually consistent with debounce). - -* **POSIX**: how POSIX compliant is the mounted fileystem? - - 0: Only the most basic features are implemented. - - 1: Some extra features are implemented. - - 2: Fully POSIX compliant. - -* **Scale**: how many hosts can be a part of the cluster? - - 0: A finite number. - - 1: A finite number of dedicated hosts, infinite ephemeral. - - 2: Infinite hosts. - -* **Failure**: how does the system handle failures (network partitions, hosts - hanging, buggy client versions)? - - 0: Data loss. - - 1: Reads and writes are halted. - - 2: Reads are allowed but writes are halted. - - 3: System is partially read/write, except effected parts. - -* **Limitations**: are there limits on how big files can be, or how big - directories can be? - - 0: Files are limited to below 1TB in size. - - 1: Directories are limited to below 100,000 files. - - 2: No limits. - -* **Encryption**: how is data encrypted? - - 0: Not at all, DIY. - - 1: Encrypted at rest. - - 2: Per-user encryption. - -* **Permissions**: how are modifications to data restricted? - - 0: Not at all. - - 1: Permissions are only superifically enforced. - - 2: Fully enforced user/group restrictions, complex patterns, and/or POSIX ACLs. - -* **Administration**: how much administration is required for the system to - function? - - 0: Frequent. - - 1: Infrequent. - - 2: Essentially none. - -* **Simplicity**: how understandable is the system as a whole? - - 0: Very complex. - - 1: Understandable with some study. - - 2: Very simple, easy to predict. - -* **Visibility**: how much visibility is available into processes within the - system? - - 0: Total black box. - - 1: Basic logging. - - 2: CLI tooling. - - 3: Exportable metrics (e.g. prometheus). - -## Evaluations - -With the rubric defined, let's start actually working through our options! There -are many, many different possibilities, so this may not be an exhaustive list. - -### [Ceph](https://docs.ceph.com/en/latest/cephfs/index.html) - -> The Ceph File System, or CephFS, is a POSIX-compliant file system built on -> top of Ceph’s distributed object store, RADOS. CephFS endeavors to provide a -> state-of-the-art, multi-use, highly available, and performant file store for -> a variety of applications, including traditional use-cases like shared home -> directories, HPC scratch space, and distributed workflow shared storage. - -- Hackability: 2. Very active community, but it's C++. -- Documentation: 2. Hella docs, very daunting. -- Transience: 0. Adding hosts seems to require multiple configuration steps. -- Priority: 1. There is fine-tuning on a per-host basis. -- Caching: 1. Clients can cache both metadata and block data. -- Conflicts: 1. The FS behaves as much like a real FS as possible. -- Consistency: 0. System is CP. -- POSIX: 2. Fully POSIX compliant. -- Scale: 2. Cluster can grow without any real bounds. -- Failure: 3. There's no indication anywhere that Ceph goes into any kind of cluster-wide failure mode. -- Limitations: 2. There are performance considerations with large directories, but no hard limits. -- Encryption: 0. None to speak of. -- Permissions: 2. POSIX ACLs supported. -- Administration: 1. This is a guess, but Ceph seems to be self-healing in general, but still needs hand-holding in certain situations (adding/removing nodes, etc...) -- Simplicity: 0. There are many moving pieces, as well as many different kinds of processes and entities. -- Visibility: 3. Lots of tooling to dig into the state of the cluster, as well as a prometheus module. - -TOTAL: 22 - -#### Comments - -Ceph has been recommended to me by a few people. It is clearly a very mature -project, though that maturity has brought with it a lot of complexity. A lot of -the complexity of Ceph seems to be rooted in its strong consistency guarantees, -which I'm confident it fulfills well, but are not really needed for the -use-case I'm interested in. I'd prefer a simpler, eventually consistent, -system. It's also not clear to me that Ceph would even perform very well in my -use-case as it seems to want an actual datacenter deployment, with beefy -hardware and hosts which are generally close together. - -### [GlusterFS](https://docs.gluster.org/en/latest/) - -> GlusterFS is a scalable network filesystem suitable for data-intensive tasks -> such as cloud storage and media streaming. GlusterFS is free and open source -> software and can utilize common off-the-shelf hardware. - -- Hackability: 2. Mostly C code, but there is an active community. -- Documentation: 2. Good docs. -- Transience: 0. New nodes cannot add themselves to the pool. -- Priority: 0. Data is distributed based on consistent hashing algo, nothing else. -- Caching: 1. Docs mention client-side caching layer. -- Conflicts: 0. File becomes frozen, manual intervention is needed to save it. -- Consistency: 0. Gluster aims to be fully consistent. -- POSIX: 2. Fully POSIX compliant. -- Scale: 2. No apparent limits. -- Failure: 3. Clients determine on their own whether or not they have a quorum for a particular sub-volume. -- Limitations: 2. Limited by the file system underlying each volume, I think. -- Encryption: 2. Encryption can be done on the volume level, each user could have a private volume. -- Permissions: 2. ACL checking is enforced on the server-side, but requires syncing of users and group membership across servers. -- Administration: 1. Beyond adding/removing nodes the system is fairly self-healing. -- Simplicity: 1. There's only one kind of server process, and the configuration of volumes is is well documented and straightforward. -- Visibility: 3. Prometheus exporter available. - -TOTAL: 23 - -#### Comments - -GlusterFS was my initial choice when I did a brief survey of DFSs for this -use-case. However, after further digging into it I think it will suffer the -same ultimate problem as CephFS: too much consistency for a wide-area -application like I'm envisioning. The need for syncing user/groups across -machines as actual system users is also cumbersome enough to make it not a -great choice. - -### [MooseFS](https://moosefs.com/) - -> MooseFS is a Petabyte Open Source Network Distributed File System. It is easy -> to deploy and maintain, highly reliable, fault tolerant, highly performing, -> easily scalable and POSIX compliant. -> -> MooseFS spreads data over a number of commodity servers, which are visible to -> the user as one resource. For standard file operations MooseFS acts like -> ordinary Unix-like file system. - -- Hackability: 2. All C code, pretty dense, but backed by a company. -- Documentation: 2. There's a giant PDF you can read through like a book. I - guess that's.... good? -- Transience: 0. Nodes must be added manually. -- Priority: 1. There's "Storage Classes". -- Caching: 1. Caching is done on the client, and there's some synchronization - with the master server around it. -- Conflicts: 1. Both update operations will go through. -- Consistency: 0. Afaict it's a fully consistent system, with a master server - being used to synchronize changes. -- POSIX: 2. Fully POSIX compliant. -- Scale: 2. Cluster can grow without any real bounds. -- Failure: 1. If the master server is unreachable then the client can't - function. -- Limitations: 2. Limits are very large, effectively no limit. -- Encryption: 0. Docs make no mention of encryption. -- Permissions: 1. Afaict permissions are done by the OS on the fuse mount. -- Administration: 1. It seems that if the topology is stable there shouldn't be - much going on. -- Simplicity: 0. There are many moving pieces, as well as many different kinds of processes and entities. -- Visibility: 2. Lots of cli tooling, no prometheus metrics that I could find. - -TOTAL: 17 - -Overall MooseFS seems to me like a poor-developer's Ceph. It can do exactly the -same things, but with less of a community around it. The sale's pitch and -feature-gating also don't ingratiate it to me. The most damning "feature" is the -master metadata server, which acts as a SPOF and only sort of supports -replication (but not failover, unless you get Pro). - -## Cutting Room Floor - -The following projects were intended to be reviewed, but didn't make the cut for -various reasons. - -* Tahoe-LAFS: The FUSE mount (which is actually an SFTP mount) doesn't support - mutable files. - -* HekaFS: Doesn't appear to exist anymore(?) - -* IPFS-cluster: Doesn't support sharding. - -* MinFS: Seems to only work off S3, no longer maintained anyway. - -* DRDB: Linux specific, no mac support. - -* BeeGFS: No mac support (I don't think? I couldn't find any indication it - supports macs at any rate). - -* NFS: No support for sharding the dataset. - -## Conclusions - -Going through the featuresets of all these different projects really helped me -focus in on how I actually expect this system to function, and a few things -stood out to me: - -* Perfect consistency is not a goal, and is ultimately harmful for this - use-case. The FS needs to propagate changes relatively quickly, but if two - different hosts are updating the same file it's not necessary to synchronize - those updates like a local filesystem would; just let one changeset clobber - the other and let the outer application deal with coordination. - -* Permissions are extremely important, and yet for all these projects are - generally an afterthought. In a distributed setting we can't rely on the OS - user/groups of a host to permission read/write access. Instead that must be - done primarily via e2e encryption. - -* Transience is not something most of these project expect, but is a hard - requirement of this use-case. In the long run we need something which can be - run on home hardware on home ISPs, which is not reliable at all. Hosts need to - be able to flit in and out of existence, and the cluster as a whole needs to - self-heal through that process. - -In the end, it may be necessary to roll our own project for this, as I don't -think any of the existing distributed file systems are suitable for what's -needed. - -[mobile_nebula]: https://github.com/cryptic-io/mobile_nebula -[nix]: https://nixos.org/manual/nix/stable/ -- cgit v1.2.3