Difference between revisions of "ALICE native xrootd"
| Ligne 12: | Ligne 12: | ||
On each xrootd server there are on or more disk partitions where the data files are stored. There is also a namespace which is a directory containing the names of the data files: theses names are the ones the redirector uses. The name itself is a symlink to the real data file. The name space can be in a separate partition or in a subdirectory of a data partition. | On each xrootd server there are on or more disk partitions where the data files are stored. There is also a namespace which is a directory containing the names of the data files: theses names are the ones the redirector uses. The name itself is a symlink to the real data file. The name space can be in a separate partition or in a subdirectory of a data partition. | ||
| − | In the case of IPNO, the namespace is always a subdir of the first data partition. | + | In the case of IPNO, the namespace is always a subdir of the first data partition. Here are some example from one xrootd server: |
| − | < | + | <pre> |
# df -h|grep xrddata | # df -h|grep xrddata | ||
/dev/sdb1 9.1T 5.6T 3.6T 62% /grid/xrddata1 | /dev/sdb1 9.1T 5.6T 3.6T 62% /grid/xrddata1 | ||
| Ligne 28: | Ligne 28: | ||
drwxr-xr-x 18 xrootd xrootd 4096 Mar 30 2015 /grid/xrddata1/namespace | drwxr-xr-x 18 xrootd xrootd 4096 Mar 30 2015 /grid/xrddata1/namespace | ||
</tt> | </tt> | ||
| + | |||
| + | The data file %grid%xrddata1%namespace%00%65278%b8f9f574-dd42-11e4-a4e6-63e8b3f6492f in the partion /grid/xrddata6 is recorded in the namespace as | ||
| + | /grid/xrddata1/namespace/00/65278/b8f9f574-dd42-11e4-a4e6-63e8b3f6492f : | ||
| + | |||
| + | <pre> | ||
| + | # ls -lh /grid/xrddata1/namespace/00/65278/b8f9f574-dd42-11e4-a4e6-63e8b3f6492f | ||
| + | lrwxrwxrwx 1 xrootd xrootd 85 Apr 7 2015 /grid/xrddata1/namespace/00/65278/b8f9f574-dd42-11e4-a4e6-63e8b3f6492f -> /grid/xrddata6/%grid%xrddata1%namespace%00%65278%b8f9f574-dd42-11e4-a4e6-63e8b3f6492f | ||
| + | |||
| + | # ls -lLh /grid/xrddata1/namespace/00/65278/b8f9f574-dd42-11e4-a4e6-63e8b3f6492f | ||
| + | -rw-rw-r-- 1 xrootd xrootd 3.6M Apr 7 2015 /grid/xrddata1/namespace/00/65278/b8f9f574-dd42-11e4-a4e6-63e8b3f6492f | ||
| + | |||
| + | </pre> | ||
Version du 11:42, 18 novembre 2015
Decommissioning ALICE native xrootd servers and dealing with data loss
Aim of this documentation
This objective of this document is to detail the procedure to follow by system administrators when they want to remove an xrootd server (decommissioning) or when they lost a filesystem on an xrootd server.
This document is based on the mails exchanged on the alice-lcg-task-force@cern.ch list and on the real cases encountered at the GRIF-IPNO site. Costin Grigoras is the author of the different recommendations and tips successfully applied at IPNO.
A quick presentation of the xrootd files tree
On each xrootd server there are on or more disk partitions where the data files are stored. There is also a namespace which is a directory containing the names of the data files: theses names are the ones the redirector uses. The name itself is a symlink to the real data file. The name space can be in a separate partition or in a subdirectory of a data partition.
In the case of IPNO, the namespace is always a subdir of the first data partition. Here are some example from one xrootd server:
# df -h|grep xrddata /dev/sdb1 9.1T 5.6T 3.6T 62% /grid/xrddata1 /dev/sdb2 9.1T 5.6T 3.6T 62% /grid/xrddata2 /dev/sdb3 9.1T 5.6T 3.6T 62% /grid/xrddata3 /dev/sdb4 9.1T 5.6T 3.6T 62% /grid/xrddata4 /dev/sdc1 9.1T 5.6T 3.6T 62% /grid/xrddata5 /dev/sdc2 9.1T 5.6T 3.6T 62% /grid/xrddata6 /dev/sdc3 9.1T 5.6T 3.6T 62% /grid/xrddata7 /dev/sdc4 9.1T 5.6T 3.6T 62% /grid/xrddata8 # # ls -ld /grid/xrddata1/namespace drwxr-xr-x 18 xrootd xrootd 4096 Mar 30 2015 /grid/xrddata1/namespace </tt> The data file %grid%xrddata1%namespace%00%65278%b8f9f574-dd42-11e4-a4e6-63e8b3f6492f in the partion /grid/xrddata6 is recorded in the namespace as /grid/xrddata1/namespace/00/65278/b8f9f574-dd42-11e4-a4e6-63e8b3f6492f : <pre> # ls -lh /grid/xrddata1/namespace/00/65278/b8f9f574-dd42-11e4-a4e6-63e8b3f6492f lrwxrwxrwx 1 xrootd xrootd 85 Apr 7 2015 /grid/xrddata1/namespace/00/65278/b8f9f574-dd42-11e4-a4e6-63e8b3f6492f -> /grid/xrddata6/%grid%xrddata1%namespace%00%65278%b8f9f574-dd42-11e4-a4e6-63e8b3f6492f # ls -lLh /grid/xrddata1/namespace/00/65278/b8f9f574-dd42-11e4-a4e6-63e8b3f6492f -rw-rw-r-- 1 xrootd xrootd 3.6M Apr 7 2015 /grid/xrddata1/namespace/00/65278/b8f9f574-dd42-11e4-a4e6-63e8b3f6492f
