Difference between revisions of "INTERNETARCHIVE.BAK/git-annex implementation"

From Archiveteam
Jump to navigation Jump to search
Line 7: Line 7:
 
Some first steps to work on:
 
Some first steps to work on:
  
* pick a set of around 10 thousand items whose size sums to around 8 TB
+
* get a list of files, checksums, and urls (done)
* build map from Item to shard. Needs to scale well to 24+ million. sql?
+
* write a script to generate a git-annex repository with 100k files from the list (done)
* write ingestion script that takes an item and generates a tarball of its non-derived files. Needs to be able to reproduce the same checksum each time run on an (unmodified) item. Note that pristine-tar etc show how to do this reproducibly.
+
 
 
* write client registration backend, which generates the client's ssh private key, git-annex UUID, and sends them to the client (somehow tied to IA library cards?)
 
* write client registration backend, which generates the client's ssh private key, git-annex UUID, and sends them to the client (somehow tied to IA library cards?)
 
* client runtime environment (docker image maybe?) with warrior-like interface (all that needs to do is configure things and get git-annex running)
 
* client runtime environment (docker image maybe?) with warrior-like interface (all that needs to do is configure things and get git-annex running)

Revision as of 21:06, 16 March 2015

This page addresses a git-annex implementation of INTERNETARCHIVE.BAK.

For more information, see http://git-annex.branchable.com/design/iabackup/.

First tasks

Some first steps to work on:

  • get a list of files, checksums, and urls (done)
  • write a script to generate a git-annex repository with 100k files from the list (done)
  • write client registration backend, which generates the client's ssh private key, git-annex UUID, and sends them to the client (somehow tied to IA library cards?)
  • client runtime environment (docker image maybe?) with warrior-like interface (all that needs to do is configure things and get git-annex running)

git-annex scalability tests

git-annex repo growth test

I made a test repo with 10000 files, added via git annex. After git gc --aggressive, .git/objects/ was 4.3M.

I wanted to see how having a fair number of clients each storing part of that and communicating back what they were doing would scale. So, I made 100 clones of the initial repo, each representing a client.

Then in each client, I picked 300 files at random to download. This means that on average, each file would end up replicated to 3 clients. I ran the downloads one client at a time, so as to not overload my laptop.

Then I had each client sync its git-annex state back up with the origin repo. (Again sequentially.) After this sync, the size of the git objects grew to 24M, gc --aggressive reduced it to 18M.

Next, I wanted to simulate maintenance stage, where clients are doing fsck every month and reporting back about the files they still have. I dummied up the data that would be generated by such a fsck, and ran it in each client (just set location log for each present file to 1). After syncing back to the origin repo, and git gc --aggressive, the size of the git objects grew to 19M, so 1MB per month growth.

Summary: Not much to worry about here. Note that if, after several years, the git-annex info in the repo got too big, git-annex forget can be used to forget old history, and drop it back down to starting levels. This leaves plenty of room to grow; either to 100k files, or to 1000 clients. And this is just simulating one share, of thousands.

Script: http://tmp.kitenet.net/git-annex-growth-test.sh