# Model levels on CDS disks **URL:** \ **Category:** C3S - Access and Login\ **Tags:** api, access, c3s, era5\ **Created:** [26 June 2021 12:35 UTC](https://forum.ecmwf.int/t/model-levels-on-cds-disks/847 "2021-06-26T12:35:04Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![Mani\_Mahdinia](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/m/74df32/32.png) [@Mani\_Mahdinia](https://forum.ecmwf.int/u/Mani_Mahdinia)\ **Post date:** [26 June 2021 12:35 UTC](https://forum.ecmwf.int/t/model-levels-on-cds-disks/847/1 "2021-06-26T12:35:04Z")
Hello everbody, I need to access ERA5 reanalysis, model levels (1/to/137), within some past times (say 1 Jan, 2015). On the webpage of [Climate Data Store (CDS) API Keywords](https://confluence.ecmwf.int/display/CKB/Climate+Data+Store+%28CDS%29+API+Keywords) only 'reanalysis-era5-complete' (on MARS) seems to have explicitly listed the model levels, but when I use this resource with the cdsapi, it just gets into queue for hours (is this due to slow data access on MARS where reanalysis-era5-complete is?). However, when I keep everything the same, but change 'reanalysis-era5-complete' to 'reanalysis-era5-pressure-levels', the job runs almost instentaniously (as the latter is available on the disks). However, I am not actually sure if 'reanalysis-era5-pressure-levels' actually has the model levels (from reanalysis, not interpolation), as it's name may suggest otherwise.  Could you let me know, if there is any way that I can get model level data (see above) from the disks? Also, is the model level (ml) data that I'm getting when I changed to 'reanalysis-era5-pressure-levels',  from interpolation or is it from reanalysis? I greatly appreciate your help and time and look forward to your reply. Mani ---
**Author:** ![Dan\_Cath](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/d/a87d85/32.png) [@Dan\_Cath](https://forum.ecmwf.int/u/Dan_Cath)\ **Post date:** [4 August 2021 22:42 UTC](https://forum.ecmwf.int/t/model-levels-on-cds-disks/847/2 "2021-08-04T22:42:18Z")
I am curious about this, too, and I am making a similar query (era5 model levels).  ---
**Author:** ![Michela](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/m/898d66/32.png) [@Michela](https://forum.ecmwf.int/u/Michela)\ **Post date:** [5 August 2021 13:57 UTC](https://forum.ecmwf.int/t/model-levels-on-cds-disks/847/3 "2021-08-05T13:57:51Z")
Hi, Due to the vast volume of these datasets (currently about 6 petabyte) ERA5 data on model levels are not stored on spinning disk, but reside in the ECMWF's MARS tape archive, instead. Access to this data is in general much slower. Please be aware that there is an additional queueing system for downloading data from the ECMWF's MARS archive -  **expect several hours to several days for submitted requests to complete ** at this time.  The ERA5 on pressure levels data are stored on disk and they are interpolated from model levels. For more details about the vertical discretisation in the ECMWF Integrated Forecasting System (IFS), please see [Part-iii Dynamics and numerical procedures, section 2.2](https://www.ecmwf.int/sites/default/files/elibrary/2015/9210-part-iii-dynamics-and-numerical-procedures.pdf) and the FULL-POS documentation at: [http://www.umr-cnrm.fr/gmapdoc/spip.php?article157](http://www.umr-cnrm.fr/gmapdoc/spip.php?article157) Thanks Michela ---
**Author:** ![Kevin\_Marsh](https://forum.ecmwf.int/user_avatar/forum.ecmwf.int/kevin_marsh/32/368_2.png) [@Kevin\_Marsh](https://forum.ecmwf.int/u/Kevin_Marsh)\ **Post date:** [5 August 2021 17:08 UTC](https://forum.ecmwf.int/t/model-levels-on-cds-disks/847/4 "2021-08-05T17:08:48Z")
Hi All, It is recommended that users use the **exact syntax**  for their CDS API requests as shown on the CDS forms for a given dataset. If you use incorrect keywords, your CDS API request may complete, but the data retrieved may not be the data expected. Hope that helps, Kevin ---
**Author:** ![Mani\_Mahdinia](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/m/74df32/32.png) [@Mani\_Mahdinia](https://forum.ecmwf.int/u/Mani_Mahdinia)\ **Post date:** [11 August 2021 02:02 UTC](https://forum.ecmwf.int/t/model-levels-on-cds-disks/847/5 "2021-08-11T02:02:41Z")
Michela and Kevin, Thanks so much for the replies. I find them very helpful. Best Regards, Mani