Hi, you have two storage pools. The calculation of the number of subblocks is performed on the system pool with 1MiB blocksize --> subblock size of 8kiB --> 128 subblocks. The other pool inherits the "128 subblocks", as all pools in a filesystem will have the same number of subblocks.
Mit freundlichen Grüssen / Best regards, Michael Hennecke HPC Chief Technologist - HPC and AI Business Unit -- Lenovo Global Technology (Germany) GmbH * Am Zehnthof 77 * D-45307 Essen * Germany Geschäftsführung: Colm Gleeson, Christophe Laurent * Sitz der Gesellschaft: Stuttgart * HRB-Nr.: 758298, AG Stuttgart From: [email protected] <[email protected]> On Behalf Of Caubet Serrabou Marc (PSI) Sent: Tuesday, 26 March, 2019 16:40 To: gpfsug main discussion list <[email protected]> Subject: [External] [gpfsug-discuss] GPFS v5: Blocksizes and subblocks Hi all, according to several GPFS presentations as well as according to the man pages: Table 1. Block sizes and subblock sizes +-------------------------------+-------------------------------+ | Block size | Subblock size | +-------------------------------+-------------------------------+ | 64 KiB | 2 KiB | +-------------------------------+-------------------------------+ | 128 KiB | 4 KiB | +-------------------------------+-------------------------------+ | 256 KiB, 512 KiB, 1 MiB, 2 | 8 KiB | | MiB, 4 MiB | | +-------------------------------+-------------------------------+ | 8 MiB, 16 MiB | 16 KiB | +-------------------------------+-------------------------------+ A block size of 8MiB or 16MiB should contain subblocks of 16KiB. However, when creating a new filesystem with 16MiB blocksize, looks like is using 128KiB subblocks: [root@merlindssio01 ~]# mmlsfs merlin flag value description ------------------- ------------------------ ----------------------------------- -f 8192 Minimum fragment (subblock) size in bytes (system pool) 131072 Minimum fragment (subblock) size in bytes (other pools) -i 4096 Inode size in bytes -I 32768 Indirect block size in bytes . . . -n 128 Estimated number of nodes that will mount file system -B 1048576 Block size (system pool) 16777216 Block size (other pools) . . . What am I missing? According to documentation, I expect this to be a fixed value, or it isn't at all? On the other hand, I don't really understand the concept 'Indirect block size in bytes', can somebody clarify or provide some details about this setting? Thanks a lot and best regards, Marc _________________________________________ Paul Scherrer Institut High Performance Computing Marc Caubet Serrabou Building/Room: WHGA/019A Forschungsstrasse, 111 5232 Villigen PSI Switzerland Telephone: +41 56 310 46 67 E-Mail: [email protected]<mailto:[email protected]>
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