* blob: changed default shards from {3,3} to {1,3}
Turns out for very large repository around 100TB (5M blobs),
we end up creating max ~16M directories which is way too much
and slows down listing. Currently each leaf directory only has a handful
of files.
Simple sharding of {3} should work much better and will end up creating
directories with meaningful shard sizes - 12 K files per directory
should not be too slow and will reduce the overhead of listing by
4096 times.
The change is done in a backwards-compatible way and will respect
custom sharding (.shards) file written by previous 0.9 builds
as well as older repositories that don't have the .shards file (which
we assume to be {3,3}).
* fixed compat tests
* blob: support for custom blob store sharding
This is experimental.
The .shards file can reside in the root of any blob storage that uses
sharding (filesystem/sftp/webdav) and can specify rules for sharding.
{
"default": [3,2,1],
"overrides": [
{ "prefix": "p", "shards": [2,2] },
{ "prefix": "x", "shards": [1,1,1] }
],
"maxNonShardedLength": 2
}
With this in place we'll be later able to do resharding of the
repository to optimize get/put/list performance for both repositories
and caches.
* cli: command line tools to manipulate shards in a directory
