dCache Tier I meeting June 22, 2009

Present

dCache.org(Gerd), IN2P3(), Sara(), Triumf(), BNL(), NDGF(), PIC(Gerard), GridKa(), Fermi(), CERN(Andrea)

Apologies

Fermi, FZK, SARA

Technical issues

None

Site reports

NDGF

Nothing to report

PIC

OK,

Fermi

(via email) Nothing to report

Questions from PIC

Gerard asked a number of questions.

Default tokens

PIC wishes to use the default token feature where if a user doesn't specify a space token then use a configured default token. Does this feature require implicit space reservations to switched on?

No; that is orthogonal.

What would happen for people who don't specify a space token and who try to write into a directory where there is no configured default space token?

If there are no matching non-linkgroup links (that is, links not in a linkgroup) into which the user can write then that user will be unable to write into a directory. The error message "no write pools available" would be recorded in the log files.

Statistics in PnfsManager

What are the meaning of the statistics in PnfsManager? The info command shows a table consisting of three columns. What do these numbers mean?

The numbers are

• the total number requests,
• the number of failed requests,
• the number of folded requests.

The total number is all requests, independent of what happened to the request. The number of failed requests is those messages where PnfsManager was unable to discover the answer.

There is a queue of pending requests in PnfsManager. It is possible that some queries are repeated later-on in the queue so that knowing the answer to the first query will (independent of the intermediate requests) result in knowing the other requests too. If this happens, then knowing the answer to the first query will result in knowing the answer to the subsequent queries. Folding is when these subsequent queries are also answered.

This is not caching the result and will only appear as an effect if PnfsManager has developed a queue.

AP/ Need to write down the criteria that a request is considered a failure.

AP/ check semantics of folding numbers; for example, by how much is the folded counter increased by if a request that is repeated 100 times completes and all 100 requests are replied with this information.

Problems with GUI

Seems to be an issue with inconsistent numbers, Patrick to follow up.

When will we have NFS in dCache

Gerard was asking about NFS: when will NFS be available?

NFS v4.1 will come with dCache v1.9.3 without ACL support. We anticipate being able to set up a dCache v1.9.3 for testing. This would require a custom Linux kernel, to include the client support for NFS.

AP/ dCache.org will supply information to Gerard on how to set up a test NFS instance.

Discovering new bugs from STEP09

From Andrea:

I would like to ask the developers if previously unknown dCache bugs were discovered in STEP'09 operations.

There were no new bugs discovered.

One item of feedback from the German Cloud was about pool-2-pool transfers to balance load. Some (Tier-2) sites were successful in using this, some had problems and disable the feature and some sites didn't attempt to use pool-to-pool.

PIC reported having a similar problem, but solved it.

DTNM

Same time, next week.