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  1. Lustre
  2. LU-1707

Add llapi_* function to return the OST/MDT count for a path.

Details

    • 10514

    Description

      It would be valuable to programmatically discover the number of OSTs that are available. An llapi_* function would be a suitable place for this call.

      Use Case

      When writing HDF5 files one typically configures the number of writers as a fraction of the number of OSTs for best performance.

      Currently this information is only available by writing a file with stripe count set to -1 and then counting the number of stripes present. A programmatic interface to the OST count would simplify this task.

      Attachments

        Issue Links

          is related to

          Bug - A problem which impairs or prevents the functions of the product. LU-2182 Add llapi_file_get_layout() function in liblustreapi

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Closed

          New Feature - A new feature of the product, which has yet to be developed. LU-3480 Layout Enhancement

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Closed

          Improvement - An improvement or enhancement to an existing feature or task. LU-5969 Create an LGPL version of liblustreapi

          • Major - Major loss of function.
          • Resolved

          Activity

            [LU-1707] Add llapi_* function to return the OST/MDT count for a path.
            simmonsja James A Simmons added a comment -

            The function  llapi_get_obd_count() does exist so we can close this.

            simmonsja James A Simmons added a comment - The function  llapi_get_obd_count() does exist so we can close this.
            adilger Andreas Dilger added a comment -

            Adding this as a requirement to LU-5969.

            adilger Andreas Dilger added a comment - Adding this as a requirement to LU-5969 .
            nedbass Ned Bass (Inactive) added a comment -

            The functionality described in the description of this issue is still lacking in the API. A set of new interfaces is needed that implements John's suggestion from this comment.

            nedbass Ned Bass (Inactive) added a comment - The functionality described in the description of this issue is still lacking in the API. A set of new interfaces is needed that implements John's suggestion from this comment.
            adilger Andreas Dilger added a comment -

            Ned, does the new llapi_layout_* functionality landed via http://review.whamcloud.com/5302 or is there still work to be done?

            adilger Andreas Dilger added a comment - Ned, does the new llapi_layout_* functionality landed via http://review.whamcloud.com/5302 or is there still work to be done?
            simmonsja James A Simmons added a comment -

            Yep, I also just had this discussion with Ned.a few minutes ago. This overlaps the work I'm doing in LU-5030 so I will get around to implementing this for you. Looks like I will have to focus my time toward LU-5030 first.

            simmonsja James A Simmons added a comment - Yep, I also just had this discussion with Ned.a few minutes ago. This overlaps the work I'm doing in LU-5030 so I will get around to implementing this for you. Looks like I will have to focus my time toward LU-5030 first.
            afn Andy Nelson added a comment -


            See my above comment of 4:42 Dec 6, 2013, re llapi_get_obd_count in the context of closing this ticket.

            afn Andy Nelson added a comment - See my above comment of 4:42 Dec 6, 2013, re llapi_get_obd_count in the context of closing this ticket.
            simmonsja James A Simmons added a comment -

            While looking at LU-2182 I noticed this ticket. This functionality has been implemented as

            int llapi_get_obd_count(char *mnt, int *count, int is_mdt)

            If this fits what you are looking for then let us know so this ticket can be closed.

            simmonsja James A Simmons added a comment - While looking at LU-2182 I noticed this ticket. This functionality has been implemented as int llapi_get_obd_count(char *mnt, int *count, int is_mdt) If this fits what you are looking for then let us know so this ticket can be closed.
            morrone Christopher Morrone (Inactive) added a comment -

            An even simpler case: A filesystem has 100 OSTs, but one is marked inactive. The function should return 99 in that case.

            morrone Christopher Morrone (Inactive) added a comment - An even simpler case: A filesystem has 100 OSTs, but one is marked inactive. The function should return 99 in that case.
            rhenwood Richard Henwood (Inactive) added a comment -

            I understand. My interpretation is now that both Andy and myself do want the 'maximum stripe count', as you suggested.

            rhenwood Richard Henwood (Inactive) added a comment - I understand. My interpretation is now that both Andy and myself do want the 'maximum stripe count', as you suggested.
            jhammond John Hammond added a comment -

            IIRC any system with more than 2000 OSTs will have this property.

            jhammond John Hammond added a comment - IIRC any system with more than 2000 OSTs will have this property.

            People

              wc-triage WC Triage
              rhenwood Richard Henwood (Inactive)
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              Dates

                Created:
                Updated:
                Resolved: