Transcript Slide - Indico

HEPiX Storage Task Force
Roger Jones
Lancaster
CHEP06, Mumbai, February 2006
Mandate
– Examine the current LHC experiment computing
models.
– Attempt to determine the data volumes, access
patterns and required data security for the various
classes of data, as a function of Tier and of time.
– Consider the current storage technologies, their prices
in various geographical regions and their suitability for
various classes of data storage.
– Attempt to map the required storage capacities to
suitable technologies.
– Formulate a plan to implement the required storage in
a timely fashion.
February 13th 2005
Membership
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-o- Roger Jones, Lancaster, ATLAS [email protected]
-o- Andrew Sansum, RAL, [email protected]
-o- Bernd Panzer/ Helge Meinhard, CERN, [email protected]
-o- David Stickland (latterly) (CMS)
-o- Peter Malzacher GSI Tier-2, Alice, [email protected]
-o- Andrei Maslennikov,CASPUR, [email protected]
-o- Jos van Wezel GridKA, HEPiX, [email protected]
• Shadow 1 [email protected]
• Shadow 2 [email protected]
• -o- Vincenzo Vagnoni Bologna, LHCb, [email protected]
• -o- Luca dell’Agnello
• -o- Kors Bos, NIKHEF by invitation
Thanks to all members!
February 13th 2005
Degree of Success
• Assessment of Computing Model
– RJ shoulders the blame for this area!
– Computing TDRs help – see many talk at this conference
– Estimates of contention etc rough; toy simulations are exactly
that, and we need to improve this area beyond the lifetime of the
task force.
• Disk
– Thorough discussion of disk issues
– Recommendations, prices etc
• Archival media
– Less complete discussion
– Final reporting here in April HEPiX/GDB meeting in Rome
• Procurement
– Useful guidelines to help tier 1 and tier 2 procurement
February 13th 2005
Outcome
• Interim document available through the GDB
• Current High Level Recommendations
– It is recommended that a better information exchange mechanism be
established between (HEP) centres to mutually improve purchase
procedures.
– An annual review should be made of the storage technologies and prices,
and a report made publicly available.
– Particular further study of archival media is required, and tests should be
made of the new technologies emerging.
– A similar regular report is required for CPU purchases. This is motivated
by the many Tier-2 centres now making large purchases.
– People should note that the lead time from announcement to effective
deployment of new technologies is up to a year.
– It is noted that the computing models assume that archived data is
available at the time of attempted processing. This implies that the
software layer allows pre-staging and pinning of data.
February 13th 2005
Inputs
• Informed by C-TDRs and computing model
documents
– Have tried to estimate contentions etc, but this
requires much more detailed simulation work
– Have looked at data classes and associated
storage/access requirements, but his could be taken
further
• E.g. models often provide redundancy on disk, but some sites
assume they still need to back disk to tape in all cases
– Have included bandwidths to MSS from LHC4 exercise,
but more detail would be good
February 13th 2005
Storage Classes
1) tape, archive, possibly offline (vault), access >
2 days, 100 MB/s
2) tape, on line in library, access > 1 hour, 400
MB/s
3) disk, any type, in front of tape caches
4) disk, SATA type optimised for large files,
sequential Read only IO
5) disk, SCSI/FC type optimised for small files,
Read/Write random IO
6) disk, high speed and reliability RAID 1 or 6
(catalogues, home directories etc)
February 13th 2005
Disk
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Two common disk types
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SCSI/FibreChannel
• Higher speed and throughput
• Little longer lifetime (~4 years)
• More expensive
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SATA (II)
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Cheaper
Available in storage arrays
Lifetime >3 years (judging by warrantees!)
RAID5 gives fair data security
–
Could still have 10TB/1PB unavailable on any given day
• RAID6 looks more secure
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Some good initial experiences
Care needed with drive and other support
Interconnects
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Today
• SATA (300 MB/s)
–
Good for disk to server, point to point
• Fibre channel (400 MB/s)
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High speed IO interconnect, fabric
Soon (2006)
• Serial Attached SCSI (SAS – multiple 300 MB/s)
• Infiniband (IBA 900 MB/s)
February 13th 2005
Architectures
• Direct Attached Storage
– Disk is directly attached to CPU
– Cheap but administration costly
• Network Attached Storage
Clients
node 1
node 1
Storage Controller
node 2
IP network
node n
– File servers on Ethernet network
– Access by file-based protocols
• Slightly more expensive but smaller number of dedicated
nodes
• Storage in a box – servers have internal disks
• Storage out of box – fiber or SCSI connected
• Storage Area Networks
– Block not file transport
– Flexible and redundant paths, but expensive
February 13th 2005
node n
Disk Data Access
• Access rates
– 50 streams per RAID group or 2 MB/s per
stream on a 1 Gbit interface
– Double this for SCSI
• Can be impaired by
– Software interface/SRM
– Non-optimal hardware configuration
• CPU, kernel, network interfaces
– Recommend 2 x nominal interfaces for read
and 3 x nominal for write
February 13th 2005
Disk Recommendations
• Storage in a box (DAS/NAS disks together with server logic
in a single enclosure)
– most storage for a fixed cost
– more experience with large SATA + PCI RAID deployments
desirable
– more expensive solutions may require less labour/be more
reliable (experiences differ)
– high quality support may be the deciding factor
• Recommendation
– Sites should declare the products they have in use
• A possible central place would be the central repository setup at
hepix.org
– Where possible, experience with trial systems should be shared
(Tier-1s and CERN have a big role here)
February 13th 2005
Procurement
Guidelines
• These come from H Meinhard
• Many useful suggestions for procurement
• May need to be modified to local rules
February 13th 2005
Disk Prices
• DAS/NAS: storage in a box (disks together with server logic in a single
enclosure)
– 13500-17800 € per usable 10 TB
• SAN/S: SATA based storage systems with high speed interconnect.
– 22000-26000 € per usable 10 TB
• SAN/F: FibreChannel/SCSI based storage systems with high speed
interconnect
– ~55000 € per usable 10 TB
• These numbers are reassuringly close to those from Pasta reviews,
but it should be noted there is a spread from geography and other
situations
• Evolution (raw disks)
– Expect Moore’s Law density increase of 1.6/year between 2006 and
2010
– Also consider effect of increase at only 1.4/year
– Cost reduction 30-40% per annum
February 13th 2005
Tape and Archival
• This area is ongoing and needs more work
– Less frequent procurements
• Disk system approaches active tape system costs by ~2008
• Note computing models generally only assume archive copies at the
production site
• Initial price indications similar to LCG planning projections
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40 CHF/TB for medium
25MB/s effective scheduled bandwidth drive + server is 15kCHF - 35 kCHF
Effective throughput is much lower for chaotic usage
6000 slot silo is ~500 kCHF
• New possibilities include spin on demand disk etc
– Needs study by T0 and T1s, should start now
– Would be brave to change immediately
February 13th 2005
Plans
• The group is now giving more consideration
to archival
– Need to do more on archival media
– General need for more discussion of storage
classes
– More detail to be added on computing model
operational details
• Final report in April
• Further task forces needed every year or so
February 13th 2005