Last modified 11 years ago Last modified on 06/08/10 17:35:33

dCache Tier I meeting June 8, 2010

[part of a series of meetings]

Present, IN2P3(), Sara(), Triumf(Simon), BNL(), NDGF(), PIC(Gerard), GridKa(Doris), Fermi(), CERN()


(see box on the other side)

Site reports


We have no new issues.

Last issue is tape production. Running 1.9.5-20 RC-1 already acknolwdge bug with dcap mover dies when there's too much activity.

Issue arose 1 week after

Restarting door solved the issue.

Tigran to send a link to a new RPM that should verify that the problem is Bug in re-reading file, but this should only happen when file is updated. PIC reported that the file may have

What is the file's last modification date? stage.conf .. last modified 2 June 11:57.


Not so bad.

Last week promised to open a bug about the SRM

Downtime changed ATLAS instance from kpwd auth method to using gridmap method. We forgot one group-and-role from the linkgroup-authorisation file. Do we need to restart the SRM after modifying this?

Adding new VO must be done in VO-role map is automatic reloaded.

Look into making this for SRM too.


80--90% .. no

empty directories: in Chimera database.

Empty but belong to admin directory.


Everything is stable. We have a few open tickets.

GridFTP doors.. has it already been included in the latest releases.

Tigran: ConcurrentModificationException. It looks like we really have a problem there. We would like to fix this in 1.9.5 and later.


Pool rebalancing

balancing more expensive / cheaper . Using migration tools concurrently.

We have new pools.

Thumpers that have a tendency to hang.

Replicating cached copies to the thumpers.

If request DDN to migrate data to these thumpers then these will fail.


Using hopping manager to replicating files into a tape-read pool, so users can access

Hopping manager is service triggered e.g. when files are written.

Can you define a poolgroup as destination? Yes.

What happens if the pool is full? The hop is lost: the transfer fails and isn't retried.



Go for migration module.


Set of pools into which data is written.

Move data into other pools

10TB pools, 30 pools.

Issue 1 migration job a week: slowly free up space on the write pools.

Different target-pool-selection criteria


We are using DDN here at DESY. Quite happy with them: better than Thor machine, but sometimes see very high latency with DDN.


1.6 GiB/s (reads) per server, we have 4 servers. IO waits due to checksumming (better with md than with lvm). Linux with XFS. writes go to Thors (30) can do 800MB/s to the local disks+nas.

What kind of filesystems,

PIC, 125TB partitions, ZFS filesystem. Thumpers hang sometimes with high load. Good for reads, but ...

BNL: using thumpers only for staging.

Support tickets for discussion

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Same time, next week.