Checksumming support in SRM implementations
From PDP/Grid Wiki
Some applications have requested the availability of checksumming support on files stored on the storage elements in the Netherlands. The first VO to request this was Atlas, but other VOs are also very interested. Unfortunately, checksumming support seems to be non-homogenously implemented across the different storage backend systems.
This Wiki page is the result of a short investigation into the checksumming differences between dCache, DPM, StoRM and CASTOR.
To store a file with a checksum in SRM I've used the commands
lcg-cr -d $SRM -l lfn:/grid/pvier/janjust/myfile file://$PWD/myfile --checksum lcg-cr -d $SRM -l lfn:/grid/pvier/janjust/myfile file://$PWD/myfile --checksum --checksum-type adler32 lcg-cr -d $SRM -l lfn:/grid/pvier/janjust/myfile file://$PWD/myfile --checksum --checksum-type md5
where $SRM points to the appropriate storage system.
Note: so-called gridftp checksums are checksums that can be calculated on-the-fly using a special GridFTP command
dCache
- srmping: v2.2 dCache production-1.9.3-3
- seems to support only adler32 checksums (which is what WLCG seems to want) ; according to Ron md5 is also support but this requires a server reconfiguration
- checksums
- are computed when the file is transferred to dCache or during a move between pool nodes.
- are stored in the dCache namespace
- can be retrieved using the srmls -l command
- gridftp checksums are not supported
DPM
- srmping: v2.2 DPM 1.7.0-5
- supports adler32, md5 and crc32 checksums
- supports only gridftp checksums; adler32 and crc32 are supported using a special DPM-DSI GridFTP plugin
- checksums
- can be computed using the lcg-get-checksum command
- are stored in the DPM namespace but can never be retrieved from there ( !! )
- are not displayed when using the srmls -l command
- are recalculated every time
StoRM
- srmping: v2.2 StoRM <FE:1.4.0-01.sl4><BE:1.4.0-00>
- supports only md5 gridftp checksums
- checksums
- can be computed using the lcg-get-checksum command; however, the command fails for large files
- are not displayed when using the srmls -l command
- are recalculated every time
CASTOR
- srmping: v2.2 CASTOR v2_7_15 2.1.7
- supports only adler32 checksums
- checksums
- are computed in the background
- cannot be specified with the --checksum option
- can be retrieved using the srmls -l command
- are stored in the CASTOR name space
- gridftp checksums are not supported
Command output
dCache
lcg-cr output:
$ lcg-cr -l /grid/pvier/janjust/my-dcache-file-checksum-adler32 -d $SRM file:/user/janjust/myfile --checksum guid:d156757d-ecca-472e-adb9-64ebefde23c4
srm-ls output:
$ srmls -l srm://srm.grid.sara.nl/pnfs/grid.sara.nl/data/pvier/generated/2009-08-22/filec00ed728-a4d9-43f2-86d8-e5d334c15648 8508 /pnfs/grid.sara.nl/data/pvier/generated/2009-08-22/filec00ed728-a4d9-43f2-86d8-e5d334c15648 space token(s) :15253459 storage type:PERMANENT retention policy:CUSTODIAL access latency:NEARLINE locality:NEARLINE - Checksum value: cd5d9820 - Checksum type: adler32 UserPermission: uid=18010 PermissionsRW GroupPermission: gid=1276 PermissionsR WorldPermission: R created at:2009/08/22 00:02:18 modified at:2009/08/22 00:02:18 - Assigned lifetime (in seconds): -1 - Lifetime left (in seconds): -1 - Original SURL: /pnfs/grid.sara.nl/data/pvier/generated/2009-08-22/filec00ed728-a4d9-43f2-86d8-e5d334c15648 - Status: null - Type: FILE
DPM
lcg-cr output:
$ lcg-cr -l /grid/pvier/janjust/my-dpm-file-checksum-adler32 -d $SRM file:/user/janjust/myfile --checksum guid:2352aac8-37b9-4cfd-ba91-5eaee71fd5f1
srm-ls output:
$ srmls -l $SRM 8508 /dpm/science.uu.nl/home/pvier/generated/2009-08-21/filefd107414-085b-4ff0-abf2-f6fdac110bc4 space token(s) :none found storage type:PERMANENT retentionpolicyinfo : null locality:ONLINE UserPermission: uid=/O=dutchgrid/O=users/O=nikhef/CN=Jan Just Keijser PermissionsRW GroupPermission: gid=pvier PermissionsRW WorldPermission: R created at:2009/08/21 23:56:27 modified at:2009/08/21 23:56:27 - Lifetime left (in seconds): -1 - Original SURL: /dpm/science.uu.nl/home/pvier/generated/2009-08-21/filefd107414-085b-4ff0-abf2-f6fdac110bc4 - Status: null - Type: FILE
StoRM
lcg-cr output:
$ lcg-cr -l /grid/pvier/janjust/my-storm-file-checksum-adler32 -d $SRM file:/user/janjust/myfile --checksum [LCG-UTIL][lcg_cr4][] Destination may be corrupted: Source checksum (cd5d9820) != Destination checksum (d41d8cd98f00b204e9800998ecf8427e ) [LCG-UTIL][lcg_cp4][] srm://srm.grid.rug.nl/pvier/generated/2009-08-21/filecc31824f-0a4a-4bd5-8a5e-7fc00cbe4aee has been DELETED, please try again (temporary network problem? ) lcg_cr: Resource temporarily unavailable
a different file:
$ lcg-cr -l /grid/pvier/janjust/my-storm-file-checksum-adler32 -d $SRM file:/user/janjust/wms_soap_msgs.txt --checksum [LCG-UTIL][lcg_cr4][] Destination may be corrupted: Source checksum (8d9e8485) != Destination checksum (d41d8cd98f00b204e9800998ecf8427e) [LCG-UTIL][lcg_cp4][] srm://srm.grid.rug.nl/pvier/generated/2009-08-22/fileddf9c6c0-f01a-46d5-b1b2-1f48fc498c87 has been DELETED, please try again (temporary network problem?) lcg_cr: Resource temporarily unavailable
Interesting: the destination checksum is the same, even though it's a completely different file ?!?!?!?!
srm-ls output: not shown as the file was not successfully copied.
CASTOR
lcg-cr output:
$ lcg-cr -d $SRM/myfile2 -l lfn:/grid/pvier/janjust/my-castor-file2 file://$PWD/myfile --checksum [LCG-UTIL][lcg_get_checksum_surls][] srm://srm-dteam.gridpp.rl.ac.uk/castor/ads.rl.ac.uk/test/dteam/disk0tape0/janjust/myfile2: Communication error on send guid:64344a07-f3f3-41e5-9079-c86bf61a874e lcg_cr: Communication error on send
Afterwards the file is stored in SRM but not in the LFC.
srmls output (after 10 minutes; the checksum calculation happens in the background):
$ srmls -l $SRM/myfile 8508 /castor/ads.rl.ac.uk/test/dteam/disk0tape0/janjust/myfile space token(s) :none found type: null retentionpolicyinfo : null locality:ONLINE_AND_NEARLINE - Checksum value: 0xcd5d9820 - Checksum type: adler32 UserPermission: uid=dteam001 PermissionsRWX GroupPermission: gid=dteam PermissionsRWX WorldPermission: RW created at:2009/08/20 17:11:06
