# API Request failing with internal MARS-server error

**URL:** <https://forum.ecmwf.int/t/api-request-failing-with-internal-mars-server-error/883>\
**Category:** API\
**Tags:** api, c3s, mars\
**Created:** [9 January 2024 18:48 UTC](https://forum.ecmwf.int/t/api-request-failing-with-internal-mars-server-error/883 "2024-01-09T18:48:01Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Christopher\_Subich](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/c/b38774/32.png) [@Christopher\_Subich](https://forum.ecmwf.int/u/Christopher_Subich)\
**Post date:** [9 January 2024 18:48 UTC](https://forum.ecmwf.int/t/api-request-failing-with-internal-mars-server-error/883/1 "2024-01-09T18:48:01Z")

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I've been downloading (among other things) surface-level information for relatively recent dates, and my download for February 2022 has failed.&nbsp; The most recent of these requests has the request ID&nbsp;f840acf6-8ed3-4ca0-8e6a-99122498a90c.&nbsp; The failure message states (after adding some whitespace for readability and eliding duplicate portions):

**The request you have submitted is not valid**

Reason:&nbsp;wmo\_read\_any\_from\_file: error -11 (Input output problem) l=67108864, len=2076588 (Illegal seek);

Mars server task finished in error;

Double buffer error: Assertion failed: length == buffers\_[i].length\_ in run, line 282 of /home/cds/git/mars-server/eckit/src/eckit/io/[DblBuffer.cc](http://DblBuffer.cc)(RemoteException from Connector[mvr0019,marsmvr-0019:49701]) [mars];

Error code is -2;

\<This repeats 5 more times\>

Request failed; Some errors reported (last error -2)

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**Author:** ![Anabelle](https://forum.ecmwf.int/user_avatar/forum.ecmwf.int/anabelle/32/360_2.png) [@Anabelle](https://forum.ecmwf.int/u/Anabelle)\
**Post date:** [10 January 2024 14:55 UTC](https://forum.ecmwf.int/t/api-request-failing-with-internal-mars-server-error/883/2 "2024-01-10T14:55:14Z")

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Please refer to this announcement for the latest updates on an ongoing issue with downloading data from the CDS:[CDS performance issue resolved following maintenance session of January 8 2024](https://forum.ecmwf.int/t/cds-performance-issue-resolved-following-maintenance-session-of-january-8-2024/1116)