Data is Customers’ Gold,
the Operating System the Bank,
the Filesystem the Vault.
Discussing “Choice” last year, I already mentioned that we are proud to have certified all primary local filesystems in SUSE Linux Enterprise 11 (ext3, xfs, reiserfs) with major storage systems, and provide the best scaling choice for storage from desktop to datacenter (SUSE Linux Enterprise 11 Service Pack 1 Specifications).
When we introduced reiserfs into SUSE Linux Enterprise Server 7 in 2000, there was no choice: no other journaling filesystem had been ready, and we were the first to support a journaling filesystem in an Enterprise Linux at all.
With SUSE Linux Enterprise Server 8 reiserfs became the default filesystem. In 2002 we also started to support xfs, at that time the only Linux filesystem to support POSIX ACLs and extended attributes.
With filesystem deployments beyond 64 TiB, xfs is still the leading local Linux filesystem with respect to scalability.
At the time reiserfs was the only choice, but it is not first choice anymore; there are other options, and as product manager you have to decide how to develop and where to go – based on market research, customer feedback and technical advice by the engineering team.
The most important argument when discussing filesystems and their support is the question of customer data, existing and future deployments:
You don’t want to leave customers in a situation where they cannot access their data anymore. That’s why SUSE Linux Enterprise Server 11 Service Pack 1 still comes with a jfs module, even though we started deprecating this filesystem with SUSE Linux Enterprise Server 10 three years ago.
The second most important question is where you want to invest, where you want to put your resources – which horse you want to bet on.
The Enterprise Linux area is special, as you are on the one hand competing with proprietary operating systems. On the other hand you are part of a community ecosystem, which you are eating from, and which you are feeding. This community does not always speak with one voice.
Back in the filesystem area now, there is an emerging trend to agree on btrfs as the local filesystem for Linux, and some non-Enterprise Linux distributions already have chosen it as their default.
When planning SUSE Linux Enterprise Server 11 two years ago, we discussed btrfs and its capabilities as part of our strategy, but btrfs is not yet stable enough to protect our customer’s gold, thus provided as a Technology Preview in SUSE Linux Enterprise Server 11 Service Pack 1; we expect btrfs to be in an enterprise-ready status end of 2011.
That said, btrfs is the direction to go. Btrfs is the horse we are investing in for the future.
On the flip side, this means that there are horses we do not bet on – and those we are not even willing to feed. Ext4 is one of those.
The table below may give you an idea why this decision is also backed by a number of technical arguments.
Feel free to comment!
Comparison ext4 vs. btrfs
|metadata format||classic unix-inode||btree items|
|metadata replication||yes, with raid||yes, native|
|data replication||yes, with raid||yes, native or with RAID|
|prioritized storage pools||no||yes|
|fs-global snapshot||yes, with lvm||yes, native|
|online ext3 conversion||yes||no|
|offline ext3 conversion||yes||yes|
|reversible ext3 conversion||no||yes|
|extensible metadata format||yes||yes|
|efficient small file storage||yes||yes|
|active community||yes||yes, strong|
Frequently asked questions
- Q 1. Which filesystem should I choose for a new deployment?
- For a discussion about different filesystems and their optimal use case, compare the recent article in Novell’s Connection Magazine “Two Paths to Server Performance — I/O scheduler and file system selection can boost SUSE Linux Enterprise server performance”.
- Q 2. SUSE Linux Enterprise Server 12 will be released about 3-4 years after SUSE Linux Enterprise Server 11, and you say that you are considering to not support creation of new reiserfs filesystems by then. Should I deploy new data on reiserfs today? Can I keep existing reiserfs filesystem?
- Yes and Yes. reiserfs for existing deployments is expected to be fully supported by SUSE Linux Enterprise Server 12, i.e., for at least 10 years from now.
- Q 3. But isn’t ext4 just “the better ext3” as ext3 was ext2 plus journaling support?
- Yes and no. There are some features in ext4 that can be used without breaking compatibility with the ext3 disk format but most useful ones require altering the file system in an incompatible manner. Since we have been offering these features using different file systems for years, we chose not to introduce potential instability with little improvement in functionality.