I can hardly remember that slides:-) Anyway, though Bestman has built-in support for Alder32, it is expensive because data has to be transferred to bestman node for the calculation. Bestman also provides a hook so that one can use an external command for Alter32, which is probably what you should look at if you are going to do a lot of transfer and Adler32 via bestman.
The idea is that xrootd itself, if configured, allow a client to query file checksum (whatever type, but not multiple types simultaneously). In this way, the checksum is calculated on the xrootd data server and only the checksum value is retuned to the client. The command xrd supports the querying of checksum and xrdadler32 supports querying of adler32 checksum.
The configuration in xrootd itself is a line like this:
xrootd.chksum max 3 adler32 /path/xrdadler32
xrdadler32 can take both a local file and a root url. So if bestman calls xrdalder32 with a root url, you will be able to return the adler32 to bestman (you will likely need a wrapper script for this since bestman it doesn't know how to transfer a file system path to root url). The following commands will help your to write such a wrapper script:
$ getfattr --only-value -n xroot.url /xrootd/atlas/usr/y/yangw/junk <== /xrootd/atlas/... is a xrootdfs filesystem path
$ xrdadler32 root://atl-xrdr:11094//atlas/xrootd/usr/y/yangw/junk
Wei Yang | [log in to unmask] | 650-926-3338(O)
On Jun 2, 2011, at 9:50 AM, Paul T. Keener wrote:
> Thanks. I am aware of that page, however (1) is isn't clear to me that
> xrootdfs supports user_xattr, which the instructions on the page require
> and (2) I have seen some indications (eg,
> ) that suggest there is some native support for checksums.
> I have not seen anything definitive on either of these two.
>> ----- Original Message -----
>> Check if this helps:
>> From: "Paul T. Keener" <[log in to unmask]>
>> Date: Thursday, June 2, 2011 11:27 am
>> Subject: Checksum support for BeStMan
>> To: xrootd-l <[log in to unmask]>
>>> I have an SE managed by BeStMan that uses an xrootdfs mounted
>>> for its filestore. What is the best way to support adler32 checksums
>>> this setup? Are user_xattr's supported to use the "usual" method or
>>> there a better way?
>>> Paul T. Keener
>>> Department of Physics and Astronomy
>>> University of Pennsylvania