--+Access Stash remotely

Overview

Stash runs on Ceph, a highly-scalable, clustered, POSIX-compliant network filesystem. You may use this feature for temporary data storage.

This page will introduce users to accessing data stored on stash remotely using HTTP and XRootD.

Stash Area

After you login to login.uscms.org, you can access your stash area as followed:

Stash is mounted on the CMS Connect login node ( login.uscms.org) at /stash, and is accessible to workers via XRootD. The portion of your Stash designated public is also available directly via HTTP.

% ssh username@login.uscms.org $ ls /stash/user/khurtado public work $ cd /stash/user/khurtado/work $ ls test.txt

Accessing Stash via HTTP

User accounts on CMS Connect have a directory that is automatically web accessible via http://stash.osgconnect.net/+username . This directory is located at /stash2/user/username/public. To make a file or directory accessible, copy it to this directory or a subdirectory of this directory and give files permissions of 644 and directories permissions of 755. E.g. :

 Browsing the public Stash area

Copying files via HTTP

You can download your files using wget easily:

$ wget --no-check-certificate http://stash.osgconnect.net/+khurtado/rootlogon.C --2015-10-30 15:56:18-- http://stash.osgconnect.net/+khurtado/rootlogon.C Resolving stash.osgconnect.net... 192.170.227.183 Connecting to stash.osgconnect.net|192.170.227.183|:80... connected. HTTP request sent, awaiting response... 302 Found Location: http://stash.osgconnect.net/+khurtado/rootlogon.C [following] --2015-10-30 15:56:18-- http://stash.osgconnect.net/+khurtado/rootlogon.C Resolving stash.osgconnect.net... 192.170.227.183 Reusing existing connection to stash.osgconnect.net:80. HTTP request sent, awaiting response... 200 OK Length: 3996 (3.9K) [text/x-c] Saving to: “rootlogon.C” 100%[===================================================================================================================================================>] 3,996 --.-K/s in 0s 2015-10-30 15:56:19 (176 MB/s) - “rootlogon.C” saved [3996/3996]

You can also use curl, for example:

$ curl -L http://stash.osgconnect.net/+khurtado/rootlogon.C > rootlogon.C % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 102 3996 102 3996 0 0 234k 0 --:--:-- --:--:-- --:--:-- 234k

--+Access Data via XRootD

Using the XRootD service (AAA) it is possible to read data stored in e.g Tier-2 Sites, CERN, Fermilab or to write to such sites if you have write permissions to do so. Please, read Section 5.13 of the CMS Offline Workbook for full instructions on how to either copy files via xrdcp or to directly open files via AAA using in CMSSW and ROOT.

Notice that in order to use this service from the CMS Connect login node you will need to:

• Setup a release of the CMSSW framework.
• Have and initialize a valid proxy certificate.

On ROOT:

TFile *f =TFile::Open("root://cmsxrootd.fnal.gov///store/mc/SAM/GenericTTbar/GEN-SIM-RECO/CMSSW_5_3_1_START53_V5-v1/0013/CE4D66EB-5AAE-E111-96D6-003048D37524.root");

Otherwise, you can use xrdcp to copy your file:

xrdcp root://cmsxrootd.fnal.gov///store/mc/SAM/GenericTTbar/GEN-SIM-RECO/CMSSW_5_3_1_START53_V5-v1/0013/CE4D66EB-5AAE-E111-96D6-003048D37524.root foo.root