https://devzone.nordicsemi.com/f/nordic-q-a/68259/fds-write-failureHi, I am seeing some random behavior on FDS write: 1.sometimes it won&#39;t receive any callback for 2 seconds 19:57:49 - logMessage: &quot;Fds_Write_Async 2&quot; 19:57:51 - logMessage: &quot;Fds_write timeout&quot; 2. sometimes it won&#39;t find the exisiting theen-USTelligent Community 13Thu, 12 Nov 2020 15:52:26 GMThttps://devzone.nordicsemi.com/thread/279795?ContentTypeID=1Thu, 12 Nov 2020 15:52:26 GMT137ad170-7792-4731-bb38-c0d22fbe4515:f2eabadf-64be-4efb-9c7a-f8507db4580cKenneth<p>Hello,</p> <p>If you are using FreeRTOS you should be aware that FDS is not thread safe by itself, so I know there are some special considerations that should be done before and after executing FDS calls. If you think it may be FreeRTOS related, I may need to transfer this case to someone with in-depth experience with FreeRTOS.&nbsp;</p> [quote user=""]1.sometimes it won&#39;t receive any callback for 2 seconds[/quote] <p>Typically flash operations have the second lowest (fourth) priority compared to other softdevice activities, see here:<br /><a href="https://infocenter.nordicsemi.com/topic/sds_s140/SDS/s1xx/multilink_scheduling/priorities_and_events_intro.html">https://infocenter.nordicsemi.com/topic/sds_s140/SDS/s1xx/multilink_scheduling/priorities_and_events_intro.html</a></p> <p>Can it be that you have other activities with high priorities that may delay or cause the flash operation to timeout? If you experience timeout you may try to increase&nbsp;NRF_FSTORAGE_SD_MAX_RETRIES.</p> <p>If the activity that prevents the flash operations to be executed immediately is stopped, you may suddenly get multiple flash operations completed in a row afterwards. They may have been queued until success.</p> <p>Best regards,<br />Kenneth</p><div style="clear:both;"></div>