Hi Aaron, By large block size we are primarily talking about block sizes 4 MB and greater. You are correct, in my previous message I neglected to mention the file create performance for small files on these larger block sizes due to the subblock change. In addition to the added space efficiency, small file creation (for example 32kB files) on large block size filesystems will improve.
In the case of a 1 MB block size, there would be no real difference in file creates. For a 16 MB block size, however there will be a performance improvement for small file creation as a part of the subblock change for new filesystems. For users who are upgrading from 4.X.X to 5.0.0, the file creation speed will remain the same after the upgrade. I hope that helps, sorry for the confusion. Thank you, Nikhil Khandelwal Spectrum Scale Development Client Adoption From: Aaron Knister <[email protected]> To: gpfsug main discussion list <[email protected]> Date: 11/29/2017 03:42 PM Subject: Re: [gpfsug-discuss] Online data migration tool Sent by: [email protected] Thanks, Nikhil. Most of that was consistent with my understnading, however I was under the impression that the >32 subblocks code is required to achieve the touted 50k file creates/second that Sven has talked about a bunch of times: http://files.gpfsug.org/presentations/2017/Manchester/08_Research_Topics.pdf http://files.gpfsug.org/presentations/2017/Ehningen/31_-_SSUG17DE_-_Sven_Oehme_-_News_from_Research.pdf http://files.gpfsug.org/presentations/2016/SC16/12_-_Sven_Oehme_Dean_Hildebrand_-_News_from_IBM_Research.pdf from those presentations regarding 32 subblocks: "It has a significant performance penalty for small files in large block size filesystems" although I'm not clear on the specific definition of "large". Many filesystems I encounter only have a 1M block size so it may not matter there, although that same presentation clearly shows the benefit of larger block sizes which is yet *another* thing for which a migration tool would be helpful. -Aaron On Wed, Nov 29, 2017 at 2:08 PM, Nikhil Khandelwal <[email protected]> wrote: Hi, I would like to clarify migration path to 5.0.0 from 4.X.X clusters. For all Spectrum Scale clusters that are currently at 4.X.X, it is possible to migrate to 5.0.0 with no offline data migration and no need to move data. Once these clusters are at 5.0.0, they will benefit from the performance improvements, new features (such as file audit logging), and various enhancements that are included in 5.0.0. That being said, there is one enhancement that will not be applied to these clusters, and that is the increased number of sub-blocks per block for small file allocation. This means that for file systems with a large block size and a lot of small files, the overall space utilization will be the same it currently is in 4.X.X. Since file systems created at 4.X.X and earlier used a block size that kept this allocation in mind, there should be very little impact on existing file systems. Outside of that one particular function, the remainder of the performance improvements, metadata improvements, updated compatibility, new functionality, and all of the other enhancements will be immediately available to you once you complete the upgrade to 5.0.0 -- with no need to reformat, move data, or take your data offline. I hope that clarifies things a little and makes the upgrade path more accessible. Please let me know if there are any other questions or concerns. Thank you, Nikhil Khandelwal Spectrum Scale Development Client Adoption _______________________________________________ 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 https://urldefense.proofpoint.com/v2/url?u=http-3A__gpfsug.org_mailman_listinfo_gpfsug-2Ddiscuss&d=DwICAg&c=jf_iaSHvJObTbx-siA1ZOg&r=WUJ15T9xHCCIfLm1wqC74jhfu28fXGLotYoHQvJlMCg&m=GNrHjCLvQL1u_WHVimX2lAlYOGPzciCFrYHGlae3h_E&s=VtVgCRl7kxNRgcl5QeHdZJ0Rz6jCA-jfQXyLztbr5TY&e=
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