['*' means complete]

Connection Management:
*v1: foolscap, no relay, live=connected-to-introducer, broadcast updates, fully connected topology
 v2: live != connected-to-introducer, connect on demand
 v3: relay?

File Encoding:
*v1: single-segment, no merkle trees
*v2: multiple-segment (LFE)
*v3: merkle tree to verify each share
*v4: merkle tree to verify each segment
 v5: only retrieve the minimal number of hashes instead of all of them

Share Encoding:
*v1: fake it (replication)
*v2: PyRS
*v2.5: ICodec-based codecs, but still using replication
*v3: C-based Reed-Solomon

URI:
*v1: really big
 v2: derive more information from version and filesize, to remove codec_name,
     codec_params, tail_codec_params, needed_shares, total_shares, segment_size

Upload Peer Selection:
*v1: permuted peer list, consistent hash
*v2: permute peers by verifierid and arrange around ring, intermixed with
     shareids on the same range, each share goes to the
     next-clockwise-available peer
 v3: reliability/goodness-point counting?
 v4: denver airport (chord)?

Download Peer Selection:
*v1: ask all peers
 v2: permute peers and shareids as in upload, ask next-clockwise peers first
     (the "A" list), if necessary ask the ones after them, etc.
 v3: denver airport?

Filetable Maintenance:
*v1: vdrive-based tree of MutableDirectoryNodes, persisted to vdrive's disk
     no accounts
 v2: move tree to client side, serialize to a file, upload,
     vdrive.set_filetable_uri (still no accounts, just one global tree)
 v3: break world up into accounts, separate mutable spaces. Maybe
     implement SSKs
 v4: filetree

Checker/Repairer:
*v1: none
 v2: centralized checker, repair agent
 v3: nodes also check their own files

Storage:
*v1: no deletion, one directory per verifierid, no owners of shares,
     leases never expire
*v2: multiple shares per verifierid [zooko]
 v3: deletion
 v4: leases expire, delete expired data on demand, multiple owners per share

UI:
*v1: readonly webish (nevow, URLs are filepaths)
*v2: read/write webish, mkdir, del (files)
 v2.5: del (directories)
 v3: PB+CLI tool.
 v3.5: XUIL?
 v4: FUSE

Operations/Deployment/Doc/Free Software/Community:
 - move this file into the wiki ?

back pocket ideas:
 when nodes are unable to reach storage servers, make a note of it, inform
 verifier/checker eventually. verifier/checker then puts server under
 observation or otherwise looks for differences between their self-reported
 availability and the experiences of others

 store filetable URI in the first 10 peers that appear after your own nodeid
 each entry has a sequence number, maybe a timestamp
 on recovery, find the newest

 multiple categories of leases:
  1: committed leases -- we will not delete these in any case, but will instead
     tell an uploader that we are full
   1a: active leases
   1b: in-progress leases (partially filled, not closed, pb connection is
       currently open)
  2: uncommitted leases -- we will delete these in order to make room for new
     lease requests
   2a: interrupted leases (partially filled, not closed, pb connection is
       currently not open, but they might come back)
   2b: expired leases

  (I'm not sure about the precedence of these last two. Probably deleting
  expired leases instead of deleting interrupted leases would be okay.)

big questions:
 convergence?
 peer list maintenance: lots of entries