LSFMM: Storage management

At the 2013 LSFMM Summit, Lukáš Czerner updated attendees on various tools for storage management. His aim was to "lessen confusion" about the tools and their status. First up was the System Storage Manager (SSM), which started out as a command-line interface to manage the Logical Volume Manager (LVM), Btrfs, device mapper (dm), storage arrays, and the like. After he created SSM, people started asking for a library interface to it, but that was outside of the scope of the project, he said.

Since then, libStorageMgmt has come about as a vendor-neutral API for managing storage. That library will be used by Blivet, which is a storage management tool that is used by Anaconda (the Fedora installer program).

Ric Wheeler asked if Czerner had worked with SUSE, so that it could also use these pieces. Hannes Reinecke noted that YaST, SUSE's installer, is modular, so it could presumably use Blivet. There is more to Blivet than just installation, however, Czerner said, as it is meant to be a post-installation management tool as well.

The idea is to create some reusable parts, like libStorageMgmt and liblvm that can be used by multiple distributions, Wheeler said. Those parts can be skinned for the particular distribution's installer (or other tool). Lots of storage vendors have been contributing to libStorageMgmt, Wheeler said.

Blivet will be able to create filesystems, Czerner said, but there was still a question over whether it should also provide a way to check filesystems (i.e. fsck). Ted Ts'o said that creating filesystems with default parameters is "really easy", but handling filesystem-specific parameters is a much harder task. In addition, filesystem check and repair is hard, at least partly because it requires asking questions of the user.

There was some discussion about the value of providing a filesystem creation interface that allowed access to advanced filesystem features. It is a difficult problem to solve as Ts'o and Dave Chinner noted. Different distributions have their own configuration for filesystem features, which can change over time, Chinner said. There is also very little value to filesystem developers for creating such an interface, Ts'o said.

Joel Becker mentioned the -T option available for mkfs for some filesystems that allows the administrator to specify a "usage type" for the filesystem. Those types get turned into a set of parameters specific to the kind of use envisioned for the filesystem (i.e. a mail server, predominantly large files, etc.). That option is really only available for ext3 and ext4, though. Since it didn't seem like there was a lot of interest in working on this problem among the filesystem and/or fstools developers, Wheeler said, that leaves it up to Blivet, YaST, and other tools to handle filesystem creation. In closing, Czerner noted that the biggest problem is fsck, which is probably not solvable in a general way.