Question ________________________________Response__________________________________
Site and Endpoints SURFsara-NIKHEF
What is the site name?  
Which endpoint URLs do your archival systems expose?
How is tape storage selected for a write (choice of endpoint, specification of a spacetoken, namespace prefix). spacetoken
What limits should clients respect? dCache related
---> Max number of outstanding requests in number of files or data volume dCache related. The tape system has no limit, but we recommend <= 1000 reqs.
---> Max submission rate for recalls or queries dCache related. The tape system has no upper limit
---> Min/Max bulk request size (srmBringOnline or equivalent) in files or data volume dCache related. The tape system has no limit but we recommend <= 20 TB
Should clients back off under certain circumstances? yes during maintanance of the dCache or tape system
---> How is this signalled to client? dCache/SRM specific
---> For which operations? recalls, stores and metadata ops.
Is it advantageous to group requests by a particular criterion (e.g. tape family, date)? No, the system will optimize recalls
---> What criterion? n.a.
Can you handle priority requests? No
---> How is this requested? n.a.
Protocol support
Are there any unsupported or partially supported operations (e.g. pinning) ?  
What timeouts do you recommend? this is dependand to the length of the tape request queue. The tape system at SURFsara is shared with all VOs and local users.
Do you have hardcoded or default timeouts? soft timeout: 4 h, hard timeout: 24 h
Operations and metrics
Can you provide total sum of data stored by VO in the archive to 100TB accuracy? yes
Can you provide space occupied on tapes by VO (includes deleted data, but not yet reclaimed space) to 100TB accuracy? yes, through dCache
How do you allocate free tape space to VOs? we don't
What is the frequency with which you run repack operations to reclaim space on tapes after data deletion? daily
Recommendations for clients
Recommendation 1  
---> Information required by users to follow advice  
Recommendation 2  
Buffer Management
Should a client stop submitting recalls if the available buffer space reaches a threshold?  
---> How can a client determine the buffer used and free space?  
---> What is the threshold (high water mark)?  
---> When should the client restart submission (low water mark)?  
If the client does not have to back off on a full buffer, and you support pinning, how is the buffer managed?  
---> Is data moved from buffer to another local disk, either by the HSM or by an external agent?  
Additional questions
Should any other questions appear in subsequent iterations of this survey?  
-- OliverKeeble - 2018-01-30
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Topic revision: r6 - 2018-04-19 - OliverKeeble
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