# Release notes for Gluster 4.1.0 This is a major release that includes a range of features enhancing management, performance, monitoring, and providing newer functionality like thin arbiters, cloud archival, time consistency. It also contains several bug fixes. A selection of the important features and changes are documented on this page. A full list of bugs that have been addressed is included further below. - [Announcements](#announcements) - [Major changes and features](#major-changes-and-features) - [Major issues](#major-issues) - [Bugs addressed in the release](#bugs-addressed) ## Announcements 1. As 4.0 was a short term maintenance release, features which have been included in that release are available with 4.1.0 as well. These features may be of interest to users upgrading to 4.1.0 from older than 4.0 releases. The 4.0 [release notes](http://docs.gluster.org/en/latest/release-notes/) captures the list of features that were introduced with 4.0. **NOTE:** As 4.0 was a short term maintenance release, it will reach end of life (EOL) with the release of 4.1.0. ([reference](https://www.gluster.org/release-schedule/)) 2. Releases that receive maintenance updates post 4.1 release are, 3.12, and 4.1 ([reference](https://www.gluster.org/release-schedule/)) **NOTE:** 3.10 long term maintenance release, will reach end of life (EOL) with the release of 4.1.0. ([reference](https://www.gluster.org/release-schedule/)) 3. Continuing with this release, the CentOS storage SIG will not build server packages for CentOS6. Server packages will be available for CentOS7 only. For ease of migrations, client packages on CentOS6 will be published and maintained. **NOTE**: This change was announced [here](http://lists.gluster.org/pipermail/gluster-users/2018-January/033212.html) ## Major changes and features Features are categorized into the following sections, - [Management](#management) - [Monitoring](#monitoring) - [Performance](#performance) - [Standalone](#standalone) - [Developer related](#developer-related) ### Management GlusterD2 #### 2. Changes to gluster based smb.conf share management Previously Gluster used to delete the entire volume share section from smb.conf either after volume is stopped or while disabling user.cifs/user.smb volume set options. With this release those volume share sections, that were added by samba hook scripts inside smb.conf, will not get removed post a volume stop or on disabling user.cifs/user.smb volume set options. Instead we add the following share specific smb.conf parameter to the end of corresponding volume share section to make it unavailable for client access: ``` available = no ``` This will make sure that the additional smb.conf parameters configured externally are retained. For more details on the above parameter search under "available (S)" at [smb.conf(5)](https://www.samba.org/samba/docs/current/man-html/smb.conf.5.html) manual page. ### Monitoring Various xlators are enhanced to provide additional metrics, that help in determining the effectiveness of the xlator in various workloads. These metrics can be dumped and visualized as detailed [here](https://docs.gluster.org/en/latest/release-notes/4.0.0/#monitoring). #### 1. Additional metrics added to negative lookup cache xlator Metrics added are: - negative_lookup_hit_count - negative_lookup_miss_count - get_real_filename_hit_count - get_real_filename_miss_count - nameless_lookup_count - inodes_with_positive_dentry_cache - inodes_with_negative_dentry_cache - dentry_invalidations_recieved - cache_limit - consumed_cache_size - inode_limit - consumed_inodes #### 2. Additional metrics added to md-cache xlator Metrics added are: - stat_cache_hit_count - stat_cache_miss_count - xattr_cache_hit_count - xattr_cache_miss_count - nameless_lookup_count - negative_lookup_count - stat_cache_invalidations_received - xattr_cache_invalidations_received #### 3. Additional metrics added to quick-read xlator Metrics added are: - total_files_cached - total_cache_used - cache-hit - cache-miss - cache-invalidations ### Performance #### 1. Support for fuse writeback cache Gluster FUSE mounts support FUSE extension to leverage the kernel "writeback cache". For usage help see `man 8 glusterfs` and `man 8 mount.glusterfs`, specifically the options `-kernel-writeback-cache` and `-attr-times-granularity`. #### 2. Extended eager-lock to metadata transactions in replicate xlator Eager lock feature in replicate xlator is extended to support metadata transactions in addition to data transactions. This helps in improving the performance when there are frequent metadata updates in the workload. This is typically seen with sharded volumes by default, and in other workloads that incur a higher rate of metadata modifications to the same set of files. As a part of this feature, compounded FOPs feature in AFR is deprecated, volumes that are configured to leverage compounding will start disregarding the option `use-compound-fops`. **NOTE:** This is an internal change in AFR xlator and is not user controlled or configurable. #### 3. Support for multi-threaded fuse readers FUSE based mounts can specify number of FUSE request processing threads during a mount. For workloads that have high concurrency on a single client, this helps in processing FUSE requests in parallel, than the existing single reader model. This is provided as a mount time option named `reader-thread-count` and can be used as follows, ``` # mount -t glusterfs -o reader-thread-count= : ``` #### 4. Configurable aggregate size for write-behind xlator Write-behind xlator provides the option `performance.aggregate-size` to enable configurable aggregate write sizes. This option enables write-behind xlator to aggregate writes till the specified value before the writes are sent to the bricks. Existing behaviour set this size to a maximum of 128KB per file. The configurable option provides the ability to tune this up or down based on the workload to improve performance of writes. Usage: ``` # gluster volume set performance.aggregate-size ``` #### 5. Adaptive read replica selection based on queue length AFR xlator is enhanced with a newer value for the option `read-hash-mode`. Providing this option with a value of `3` will distribute reads across AFR subvolumes based on the subvol having the least outstanding read requests. This helps in better distributing and hence improving workload performance on reads, in replicate based volumes. ### Standalone #### 1. Thin arbiter quorum for 2-way replication **NOTE:** This feature is available only with GlusterD2 - What is it? - How to configure/setup? - How to convert an existing 2-way to thin-arbiter? - Better would be to add all these to gluster docs and point to that here, with a short introduction to the feature, and its limitations at present. #### 2. Automatically configure backup volfile servers in clients **NOTE:** This feature is available only with GlusterD2 Clients connecting and mounting a Gluster volume, will automatically fetch and configure backup volfile servers, for future volfile updates and fetches, when the initial server used to fetch the volfile and mount is down. When using glusterd, this is achieved using the FUSE mount option `backup-volfile-servers`, and when using GlusterD2 this is done automatically. #### 3. Python code base is now python3 compatible All python code in Gluster that are installed by the various packages are python3 compatible. #### 4. (c/m)time equivalence across replicate and disperse subvolumes Enabling the utime feature, enables Gluster to maintain consistent change and modification time stamps on files and directories across bricks. This feature is useful when applications are sensitive to time deltas between operations (for example tar may report "file changed as we read it"), to maintain and report equal time stamps on the file across the subvolumes. To enable the feature use, ``` # gluster volume set features.utime ``` **Limitations**: ### Developer related #### 1. New API for acquiring leases and acting on lease recalls A new API to acquire a lease on an open file and also to receive callbacks when the lease is recalled, is provided with gfapi. Refer to the [header](https://github.com/gluster/glusterfs/blob/release-4.1/api/src/glfs.h#L1112) for details on how to use this API. #### 2. Extended language bindings for gfapi to include perl See, [libgfapi-perl](https://github.com/gluster/libgfapi-perl) - Libgfapi bindings for Perl using FFI ## Major issues **None** ## Bugs addressed Bugs addressed since release-4.0.0 are listed below.