Tags:
tag this topic
create new tag
view all tags
---+ The PPD dCache Storage Element DCache is the main disk storage system in us on the PPD Unix/Linux systems. It allows us to aggregate the storage space on many servers and present this as a unified namespace to users. Files in dCache can be read using the SRM "grid" protocol or the "local" protocols dcap and xrootd. For writing files only the SRM grid protocolcan be used and requires you to have a valid voms proxy for a supported VO. The dCache namespace can also be browsed like a normal filesystem on the PPD linux nodes but the contents of the files cannot be accessed through this (i.e. ls or find will work cp, open or mv will fail). VOs and/or groups have area to store files under their name dCache namespace in /pnfs/pp.rl.ac.uk/data/ ---++ Inspecting a file using the pnfs mount Simply use ls as you would with a local file. ls -l /pnfs/pp.rl.ac.uk/data/vo/path/to/file ---++ Converting a local file path in PNFS to a URL to access the file For srm add =srm://heplnx204.pp.rl.ac.uk= to the path beginning /pnfs i.e. =srm://heplnx204.pp.rl.ac.uk/pnfs/pp.rl.ac.uk/data/vo/path/to/file= For dcap add dcap://dcap.pp.rl.ac.uk to the path beginning /pnfs i.e. =dcap://dcap.pp.rl.ac.uk/pnfs/pp.rl.ac.uk/data/vo/path/to/file= Note that the hosts are different <font color="crimson">heplnx204</font>.pp.rl.ac.uk for srm and %RED%dcap%ENDCOLOR%.pp.rl.ac.uk for dcap ---++ Copying/Reading a file using the Grid tools To copy a file into dCache without registering it in a Logical File Catalogue =lcg-cp -v file:/path/to/local/file srm://heplnx204.pp.rl.ac.uk/pnfs/pp.rl.ac.uk/data/vo/path/to/put/file= To copy a file into dCache and register it with a Logical File Catalogue use the =lcg-cr= command instea, VOs that use the LFC may have some rules about how the LFC namespace and the SRM namespace should be related to one another. ---++ Reading a file using local protocols copying a file out of dCache using dcap: =dccp dcap://dcap.pp.rl.ac.uk/pnfs/pp.rl.ac.uk/data/vo/path/to/your/file ./file= Or, if pnfs is locally mounted: =dccp /pnfs/pp.rl.ac.uk/data/vo/path/to/your/file ./file= Access a file directly from dCache using root: =xrdcp root://dcap.pp.rl.ac.uk///pnfs/pp.rl.ac.uk/data/vo/path/to/your/file ./file= ---++ Deleting a file from dCache If the file is not registered in the LFC: =lcg-del -l srm://heplnx204.pp.rl.ac.uk/pnfs/pp.rl.ac.uk/data/vo/path/to/file= If it is registered in the LFC remove the "-l" option: =lcg-del srm://heplnx204.pp.rl.ac.uk/pnfs/pp.rl.ac.uk/data/vo/path/to/file= -- Main.ChrisBrew / Main.RobHarper - 2010-03-12
E
dit
|
A
ttach
|
Watch
|
P
rint version
|
H
istory
: r10
<
r9
<
r8
<
r7
<
r6
|
B
acklinks
|
V
iew topic
|
Ra
w
edit
|
M
ore topic actions
Topic revision: r10 - 2013-07-22
-
ChrisBrew
Home
Site map
Atlas web
CMS web
Computing web
Documentation web
PPDITForum web
LHCb web
Main web
PPDLabSpace web
Sandbox web
TWiki web
Documentation Web
Create New Topic
Index
Search
Changes
Notifications
RSS Feed
Statistics
Preferences
P
View
Raw View
Print version
Find backlinks
History
More topic actions
Edit
Raw edit
Attach file or image
Edit topic preference settings
Set new parent
More topic actions
Account
Log In
Register User
E
dit
A
ttach
Copyright © 2008-2024 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding TWiki?
Send feedback