Hi, Kevin, (reproducing mainly what I've learned from Yuri) a 512B inode can hold about 32 Disk Addresses (DAs) addressing 32 physical disk blocks (but mind: if max replication - not necessarily actual repl. -- is set to more than 1, that mans for example 16 logical blocks (R=2). A DA is 12 bytes. With a 4k inode you can expect the other 3.5kiB to contain also DAs throughout (about 298)
So with R=2 (even if actual replication is r=1), a 4k inode can hold max about 330 DAs addressing 165 logical blocks The max file size w/out indirect addressing is thus 165 x blocksize (e.g. 1320MiB @8MiB) However, there could be other data structures in an inode (EAs) reducing the space available for DAs Hence, YMMV Mit freundlichen Grüßen / Kind regards Dr. Uwe Falke IT Specialist High Performance Computing Services / Integrated Technology Services / Data Center Services ------------------------------------------------------------------------------------------------------------------------------------------- IBM Deutschland Rathausstr. 7 09111 Chemnitz Phone: +49 371 6978 2165 Mobile: +49 175 575 2877 E-Mail: [email protected] ------------------------------------------------------------------------------------------------------------------------------------------- IBM Deutschland Business & Technology Services GmbH / Geschäftsführung: Thomas Wolter, Sven Schooß Sitz der Gesellschaft: Ehningen / Registergericht: Amtsgericht Stuttgart, HRB 17122 From: "Buterbaugh, Kevin L" <[email protected]> To: gpfsug main discussion list <[email protected]> Date: 01/23/2018 08:26 PM Subject: Re: [gpfsug-discuss] Metadata only system pool Sent by: [email protected] Hi All, This is all making sense and I appreciate everyone?s responses ? and again I apologize for not thinking about the indirect blocks. Marc - we specifically chose 4K inodes when we created this filesystem a little over a year ago so that small files could fit in the inode and therefore be stored on the metadata SSDs. This is more of a curiosity question ? is it documented somewhere how a 4K inode is used? I understand that for very small files up to 3.5K of that can be for data, but what about for large files? I.e., how much of that 4K is used for block addresses (3.5K plus whatever portion was already allocated to block addresses??) ? or what I?m really asking is, given 4K inodes and a 1M block size how big does a file have to be before it will need to use indirect blocks? Thanks again? Kevin On Jan 23, 2018, at 1:12 PM, Marc A Kaplan <[email protected]> wrote: If one were starting over, it might make sense to use a smaller inode size. I believe we still support 512, 1K, 2K. Tradeoff with the fact that inodes can store data and EAs. From: "Uwe Falke" <[email protected]> To: gpfsug main discussion list <[email protected]> Date: 01/23/2018 04:04 PM Subject: Re: [gpfsug-discuss] Metadata only system pool Sent by: [email protected] rough calculation (assuming 4k inodes): 350 x 10^6 x 4096 Bytes=1.434TB=1.304TiB. With replication that uses 2.877TB or 2.308TiB As already mentioned here, directory and indirect blocks come on top. Even if you could get rid of a portion of the allocated and unused inodes that metadata pool appears bit small to me. If that is a large filesystem there should be some funding to extend it. If you have such a many-but-small-files system as discussed recently in this theatre, you might still beg for more MD storage but that makes than a larger portion of the total cost (assuming data storage is on HDD and md storage on SSD) and that again reduces your chances. Mit freundlichen Grüßen / Kind regards Dr. Uwe Falke IT Specialist High Performance Computing Services / Integrated Technology Services / Data Center Services ------------------------------------------------------------------------------------------------------------------------------------------- IBM Deutschland Rathausstr. 7 09111 Chemnitz Phone: +49 371 6978 2165 Mobile: +49 175 575 2877 E-Mail: [email protected] ------------------------------------------------------------------------------------------------------------------------------------------- IBM Deutschland Business & Technology Services GmbH / Geschäftsführung: Thomas Wolter, Sven Schooß Sitz der Gesellschaft: Ehningen / Registergericht: Amtsgericht Stuttgart, HRB 17122 From: "Buterbaugh, Kevin L" <[email protected]> To: gpfsug main discussion list <[email protected]> Date: 01/23/2018 06:17 PM Subject: [gpfsug-discuss] Metadata only system pool Sent by: [email protected] Hi All, I was under the (possibly false) impression that if you have a filesystem where the system pool contains metadata only then the only thing that would cause the amount of free space in that pool to change is the creation of more inodes ? is that correct? In other words, given that I have a filesystem with 130 million free (but allocated) inodes: Inode Information ----------------- Number of used inodes: 218635454 Number of free inodes: 131364674 Number of allocated inodes: 350000128 Maximum number of inodes: 350000128 I would not expect that a user creating a few hundred or thousands of files could cause a ?no space left on device? error (which I?ve got one user getting). There?s plenty of free data space, BTW. Now my system pool is almost ?full?: (pool total) 2.878T 34M ( 0%) 140.9M ( 0%) But again, what - outside of me creating more inodes - would cause that to change?? Thanks? Kevin ? Kevin Buterbaugh - Senior System Administrator Vanderbilt University - Advanced Computing Center for Research and Education [email protected] - (615)875-9633 _______________________________________________ gpfsug-discuss mailing list gpfsug-discuss at spectrumscale.org https://urldefense.proofpoint.com/v2/url?u=http-3A__gpfsug.org_mailman_listinfo_gpfsug-2Ddiscuss&d=DwIFAw&c=jf_iaSHvJObTbx-siA1ZOg&r=cvpnBBH0j41aQy0RPiG2xRL_M8mTc1izuQD3_PmtjZ8&m=8WgQlUnhzFycOZf-YvqYpdUkCiyEdRvWukE-KKRuFbE&s=aCywbK-1heVHPR8Fg74z9VxkGbNfCxMdtEKIDMWVIwI&e= _______________________________________________ gpfsug-discuss mailing list gpfsug-discuss at spectrumscale.org https://urldefense.proofpoint.com/v2/url?u=http-3A__gpfsug.org_mailman_listinfo_gpfsug-2Ddiscuss&d=DwIFAw&c=jf_iaSHvJObTbx-siA1ZOg&r=cvpnBBH0j41aQy0RPiG2xRL_M8mTc1izuQD3_PmtjZ8&m=8WgQlUnhzFycOZf-YvqYpdUkCiyEdRvWukE-KKRuFbE&s=aCywbK-1heVHPR8Fg74z9VxkGbNfCxMdtEKIDMWVIwI&e= _______________________________________________ gpfsug-discuss mailing list gpfsug-discuss at spectrumscale.org https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fgpfsug.org%2Fmailman%2Flistinfo%2Fgpfsug-discuss&data=02%7C01%7CKevin.Buterbaugh%40vanderbilt.edu%7C77fefde14ec54e04b35708d5629550bd%7Cba5a7f39e3be4ab3b45067fa80faecad%7C0%7C0%7C636523315820548341&sdata=rbazh5e%2BxgHGvgF65VHTs9Hf4kk9EtUizsb19l5rr7U%3D&reserved=0 _______________________________________________ gpfsug-discuss mailing list gpfsug-discuss at spectrumscale.org http://gpfsug.org/mailman/listinfo/gpfsug-discuss _______________________________________________ gpfsug-discuss mailing list gpfsug-discuss at spectrumscale.org http://gpfsug.org/mailman/listinfo/gpfsug-discuss
