On Dec 09 2015, Daniel Jagszent <[email protected]> wrote:
> AFAIK S3QL does not do directory/bucket/container listings on the Swift
> backend. So it does not matter if there are thousands or millions of
> data blocks on your Swift storage.

Well, fsck.s3ql does such listings. But they are paginated, so there
should be no issues.

> I opted to not use that filesystem anymore because S3QL and the backup
> application that filled up that filesystem (Burp, http://burp.grke.org/)
> are not a good fit. At the end the filesystem had 16 million directory
> entries and 1.5 million inodes (Burp uses hard links excessively) and
> the sqlite database that S3QL uses to store the filesystem structure was
> 1.2 GB uncompressed.

This is not unreasonable though. Note that ext4 would require at least 5
GB of metadata as well - just to store the inodes (assuming 4096 bytes
inode size). That's not yet counting directory entry *names*.


> Also S3QL scales not very good with parallel file accesses but Burp
> does a ton of those. (The sqlite database is not thread safe and thus
> every read/write access to the database gets serialized by S3QL).

Both is true, but one is not the cause of another. Most reads/writes
don't require access to the database and could run in parallel. However,
S3QL itself is mostly single threaded at the moment so the requests are
indeed serialized.

However, I have plans in the drawer to fix this at some point. The idea
is to handle reads/writes for blocks that are already cached entirely at
the C level. This will allow concurrenty *and* at the same time boost
single-threaded performance as well. Just need to find the time...


Best,
-Nikolaus

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