Hi all, Earlier we announced a logical volume manager with parallel scaling out on local hosts, which is different from the traditional RAID arrays and is more like volume managers of networking file systems: https://reiser4.wiki.kernel.org/index.php/Logical_Volumes_Background Here we provide some numbers for the latest Reiser5 software release. Note that performance of volume operations have different topicality. E.g. performance of device removal is more topical than performance of adding a device. Indeed, user usually wants the deleted device to go to other needs immediately, whereas, when adding a device he gets more disk space immediately after issuing the command (there is no need to wait for rebalancing completion). Hardware: Dell OptiPlex 7050 6C2XR, Intel Core i7-7700, 16GB RAM (4 Cores / 8 Threads) Storage media: DEV1: Lite-On LCS-256M6S, SSD 256GB, SATAIII, 2.5" DEV2: Intenso 2.5" SSD TOP, 256G, SATAIII, 2.5" DEV3: Intenso 2.5" SSD TOP, 256G, SATAIII, 2.5" DEV4: Intenso M.2 SSD TOP, 256G, SATAIII, m.2 2280 RAM0: Block device in RAM Software: Reiser4-for-5.16.patch (software release 5.1.3), download at: https://sourceforge.net/projects/reiser4/files/v5-unstable/kernel/reiser4-for-5.16.patch.gz/download Reiser4progs-2.0.5 (software release 5.1.3), download at: https://sourceforge.net/projects/reiser4/files/v5-unstable/progs/reiser4progs-2.0.5.tar.gz/download Sequential RAW operations Data set: 10G at zero offset 1. Read from RAW device Device Speed, M/s DEV1 470 DEV2 530 2. Write to RAW device Device Speed, M/s DEV1 390 DEV2 420 Sequential file operations Stripe size: 128K Data set: one 10G file 1. Read/Write a large file, Speed (M/s) Nr of Disks in the Volume Write Read 1 (DEV1) 380 460 1 (DEV2) 410 518 2 (DEV1+DEV2) 695 744 3 (DEV1+DEV2+DEV3) 890 970 4 (DEV1+DEV2+DEV3+DEV4) 950 1100 2. Copy data from/to formatted device From device To device Speed (M/s) DEV1 DEV2 260 DEV2 DEV1 255 Volume operations Stripe size: 128K Data set: one 10G file Speed of any volume operation is defined as D/T, where D - total amount of data stored on the volume T - operation time (including full data rebalancing/migration and sync) Caches are dropped before each operation. More details about logical volumes management can be found here: https://reiser4.wiki.kernel.org/index.php/Logical_Volumes_Administration 1. Adding a device to a logical volume Volume Device to add Speed M/s DEV1 DEV2 284 DEV1+DEV2 DEV3 457 DEV1+DEV2+DEV3 DEV4 574 2. Removing a device from a logical volume Volume Device to remove Speed M/s DEV1+DEV2+DEV3+DEV4 DEV4 890 DEV1+DEV2+DEV3 DEV3 606 DEV1+DEV2 DEV2 336 3. Flushing a proxy device More details about proxy device management can be found here: https://reiser4.wiki.kernel.org/index.php/Proxy_Device_Administration Before each operation all data of the logical volume are on the proxy device. After the operation all the data are on the permanent storage denoted as "Volume". Volume Proxy device Speed M/s DEV1 DEV4 228 DEV1+DEV2 DEV4 244 DEV1+DEV2+DEV3 DEV4 290 DEV1 RAM0 283 DEV1+DEV2 RAM0 301 DEV1+DEV2+DEV3 RAM0 374 DEV1+DEV2+DEV3+DEV4 RAM0 427 4. Migrating a file More details about file migration in Reiser5 volumes can be found here: https://reiser4.wiki.kernel.org/index.php/Transparent_File_Migration Before each operation all data of the file are fairly distributed among all devices-components of the logical Volume. After the operation all file's data are stored on the Target device. Volume Target Device Speed M/s DEV1+DEV2+DEV3+DEV4 DEV1 387 DEV1+DEV2+DEV3 DEV1 403 DEV1+DEV2 DEV1 427 Comment. With increasing number of components, the speed of file migration approaches (from top) the write speed to the formatted device DEV1 (380 M/s). Comments Parallel O(1)-defragmentor of compound Reiser5 volumes is in plans! Proxy devices are also a subject of defragmentation. All file and volume operations are a subject of further performance improvements. Currently IO requests against devices-components of a logical volume are submitted by the same thread. This serialization factor leads to performance drop. Once the software stability reaches beta level, the things should be parallelized. Also currently for simplicity _all_ data are read from the volume during its re-balancing. It would be more reasonable to read only those data which are a subject of migration. Theoretical limit for the speed of adding(removing) a second device is a double copy speed from DEV1 to DEV2 (respectively from DEV2 to DEV1). Currently we have respectively 1.1 and 1.3 of the copy speed.
