Data Challenges I'm Struggling With Jim Gray, Microsoft Research 1.Sneakernet is probably the best way to moving WAN data at 1GBps File transfer efforts.

Data Challenges I'm Struggling With

Jim Gray, Microsoft Research 1. Sneakernet is probably the best way to moving WAN data at 1GBps

File transfer efforts are currently 550MBps via Internet2. How to manage the multi-petybyte file repository we are about to generate.

2. The TerraServer has evolved from a mainframe to a bunch of bricks. The new design has been operating for a year and we are quite pleased with it. But we face "how-do-you-manage a bunch?" and what the best geoplex strategy?.

3. The SkyServer website is built using database technology and web services. Now moving the web services inside the database. Others are working to design a scale-out version of the server. There are several interesting data challenges in these changes.

4. Using relational tuples to represent spatial volumes as constraints. Point-in-polygon and polygon-overlap queries can then be quickly evaluated. I will briefly describe this idea.

How Do You Move A Terabyte?

14 minutes6172001,920,0009600OC 192

2.2 hours1000Gbps

1 day100100 Mpbs

14 hours97631649,000155OC3

2 days2,01065128,00043T3

2 months2,4698001,2001.5T1

5 months360117500.6Home DSL

6 years3,0861,000400.04Home phone

Time/TB$/TBSent

$/MbpsRent

$/monthSpeedMbps

Context

Source: TeraScale Sneakernet, Source: TeraScale Sneakernet, Microsoft Technical Report May 2002, MSR-TR-2002-54 http://research.microsoft.com/research/pubs/view.aspx?tr_id=569

Moving Data Bricks• WAN costs >> 100$/Mbps/month

>> 1$/GB • Beowulf networking

10,000x cheaper than WAN factors of 105 matter.

• The cheapest and fastest way to move a Terabyte cross country is sneakernet.24 hours = 4 MB/s50$ shipping vs 1,000$ wan cost.

Giga Byte Per Second File Mover• CERN to Pasadena

– Windows TCP/IP stack improvements– Opteron demo– Disk-to-Disk at 550MBps now (~2 TB/Hour)

• What we learned:– Linux tcp stack is good/better at high perf

we are catching up.– NTFS is better than various Linux FS– Near the PCI-X limit– Good way to engage the community.

• GOAL: 1GBps disk-to-disk.

OC192 = 9.9 Gbps

CERN-Caltech Trasfer SpeedsNewisys->Newisys

0

100

200

300

400

500

600

700

800

900

1000

Mar-04 May-04 Jun-04 Aug-04 Sep-04

MB

ps

File Transfer MBps1 Stream tcp MBps

PCI -X limit

tcp limit

But then what?Managing Petabytes

• CERN files are 30MB

• They produce 1 B files/year.

• How name them?

• How manage them?

• Depends on workload: how use them.

• It’s a DB problem.

Data Challenges I'm Struggling With

Jim Gray, Microsoft Research 1. Sneakernet is probably the best way to moving WAN data at 1GBps

File transfer efforts are currently 550MBps via Internet2. How to manage the multi-petybyte file repository we are about to generate.

2. The TerraServer has evolved from a mainframe to a bunch of bricks. The new design has been operating for a year and we are quite pleased with it. But we face "how-do-you-manage a bunch?" and what the best geoplex strategy?.

3. The SkyServer website is built using database technology and web services. Now moving the web services inside the database. Others are working to design a scale-out version of the server. There are several interesting data challenges in these changes.

4. Using relational tuples to represent spatial volumes as constraints. Point-in-polygon and polygon-overlap queries can then be quickly evaluated. I will briefly describe this idea.

KVM / IPKVM / IP

TerraServer – What’s new• Web Service and Web Server• New ~1 ft2/pixel full color image

of 120 urban areas• Storage Bricks

– Commodity servers”– 4 TB raw / 2 TB Raid1 SATA storage– Dual 2 GHz + 4GB RAM– 3 Bricks = TerraServer data – Data partitioned – Moving to Yukon– Working on low TCO

auto-manage • Low Cost Availability Pair & Spare

– RAID1 Mirroring– Mirrored Bunches (Yukon log ship?) – Spare Brick– Web Application

• Load balances mirrors• Uses surviving database on failure

TerraServer Challenges

• Best Geoplex strategy?

• Moving Web Services into the DB?

• Managing bunches (lower TCO).

Data Challenges I'm Struggling With

Jim Gray, Microsoft Research 1. Sneakernet is probably the best way to moving WAN data at 1GBps

File transfer efforts are currently 550MBps via Internet2. How to manage the multi-petybyte file repository we are about to generate.

2. The TerraServer has evolved from a mainframe to a bunch of bricks. The new design has been operating for a year and we are quite pleased with it. But we face "how-do-you-manage a bunch?" and what the best geoplex strategy?.

3. The SkyServer website is built using database technology and web services. Now moving the web services inside the database. Others are working to design a scale-out version of the server. There are several interesting data challenges in these changes.

4. Using relational tuples to represent spatial volumes as constraints. Point-in-polygon and polygon-overlap queries can then be quickly evaluated. I will briefly describe this idea.

Skyserver

• Personal DB

Quick Overview (Services) • SkyServer (skyserver.sdss.org)

– Web site delivers Sloan Digital Sky Survey data– Also has education– 1,000x less popular than Terraserver,

but HUGE for a science website.• A Batch Job System with Personal DBs

– Lets users run jobs http://casjobs.sdss.org/CasJobs/– Parameters & Answers to & from Personal DB– Simple batch job scheduler.

• Web Services: http://www.voservices.org/

– Photographic objects– Spectrographic objects– Transformation functions– 7 out of the 8 are .NET.

Quick Overview (Integration)• SkyQuery (http://skyquery.net/)

Distributed Query portal using web services• Archives: Pasadena, Chicago, Baltimore, Cambridge (England)

• Has grown from 4 to 20 archives,½ day to add new one (adapt DB and register with Portal) becoming international standard

2MASS

INT

SDSS

FIRST

SkyQueryPortal

ImageCutout

• Each SkyNode publishes – Schema Web Service– Database Web Service

• Portal– Plans Query (2 phase) – Integrates answers– Is itself a web service

Challenges

• Parallel data search (data pump).How to partition?How manage load

• Moving web services to DB What is the right approach?

• Move objects into DBSpatial access methodsData analysis in the DB.

Data Challenges I'm Struggling With

Jim Gray, Microsoft Research 1. Sneakernet is probably the best way to moving WAN data at 1GBps

File transfer efforts are currently 550MBps via Internet2. How to manage the multi-petybyte file repository we are about to generate.

2. The TerraServer has evolved from a mainframe to a bunch of bricks. The new design has been operating for a year and we are quite pleased with it. But we face "how-do-you-manage a bunch?" and what the best geoplex strategy?.

3. The SkyServer website is built using database technology and web services. Now moving the web services inside the database. Others are working to design a scale-out version of the server. There are several interesting data challenges in these changes.

4. Using relational tuples to represent spatial volumes as constraints. Point-in-polygon and polygon-overlap queries can then be quickly evaluated. I will briefly describe this idea.

A Detail: 3 Ways We Do Spatial?• Hierarchical mesh (extension to SQL)

– Uses table valued stored procedures– Acts as a new “spatial access method”– Porting to Yukon CLR for a 10x speedup.

• Zones: fits SQL like a glove– Amazingly simple, amazingly good.

• Constraints: a really novel idea– Lets us do algebra on regions.

• Paper:There Goes the Neighborhood: Relational Algebra for Spatial Data Search

• Idea in backup slides.

Equations Define Subspaces

• For (x,y) above the lineax+by > c

• Reverse the space by-ax + -by > -c

• Intersect a 3 volumes: a1x + b1y > c1

a2x + b2y > c2

a3x + b3y > c3

x

y

x=c/a

y=c/b

ax + by = c

x

y

Domain is Union of Convex Hulls

• Simple volumes are unions of convex hulls.

• Higher order curves also work

• Complex volumes have holes and their holes have holes. (that is harder).

Not a convex hull

+

Now in Relational Termscreate table HalfSpace (

domainID int not null -- domain name foreign key references Domain(domainID), convexID int not null, -- grouping a set of ½ spaces halfSpaceID int identity(), -- a particular ½ space x float not null, -- the (a,b,..) parameters y float not null, -- defining the ½ space z float not null, c float not null, -- the constant (“c” above) primary key (domainID, convexID, halfSpaceID)

(x,y,z) inside a convex if it is inside all lines of the convex(x,y,z) inside a convex if it is NOT OUTSIDE ANY line of the convex

select convexID -- return the convex hullsfrom HalfSpace -- from the constraintswhere @x * x + @y * y + @x * z < l -- point outside the line?group by all convexID -- consider all the lines of a

convexIDhaving count(*) = 0 -- count outside == 0

The Algebra is Simple (Boolean)@domainID = spDomainNew (@type varchar(16), @comment varchar(8000))@convexID = spDomainNewConvex (@domainID int)@halfSpaceID = spDomainNewConvexConstraint (@domainID int, @convexID int, @x float, @y float, @z float, @l float)@returnCode = spDomainDrop(@domainID)

select * from fDomainsContainPoint(@x float, @y float, @z float) Once constructed they can be manipulated with the Boolean operations.@domainID = spDomainOr (@domainID1 int, @domainID2 int, @type varchar(16), @comment varchar(8000))@domainID = spDomainAnd (@domainID1 int, @domainID2 int, @type varchar(16), @comment varchar(8000))@domainID = spDomainNot (@domainID1 int, @type varchar(16), @comment varchar(8000))

What! No Bounding Box?

• Bounding box limits search.A subset of the convex hulls.

• If query runs at 3M halfspace/sec then no need for bounding box, unless you have more than 10,000 lines.

• But, if you have a lot of half-spaces then bounding box is good.

HTM Approach• Table-valued function

find points near a point– Select * from fGetNearbyEq(ra,dec,r)

• Use Hierarchical Triangular Mesh www.sdss.jhu.edu/htm/

– Space filling curve, bounding triangles…– Standard approach

• 13 ms/call… So 70 objects/second.• Too slow, so precompute neighbors:

Materialized view.• At 70 objects/sec

it takes 6 months to compute a billion objects.

Zone Approach• Divide space into zones• Key points by Zone, offset

(on the sphere this need wrap-around margin.)

• Point search look in a few zonesat a limited offset: ra ± ra bounding box that has

1-π/4 false positives• All inside the relational engine• Avoids “impedance mismatch” • Can “batch” all-all comparisons• 33x faster and parallel

6 days, not 6 months!

r ra-zoneMax

√(r2+(ra-zoneMax)2)cos(radians(zoneMax))

zoneMax

x

Ra ± x

In SQL

select o1.objID -- find objectsfrom zone o1 -- in the zoned tablewhere o1.zoneID between -- where zone #

floor((@dec-@r)/@zoneHeight) and -- overlaps the circlefloor((@dec+@r)/@zoneHeight)

and o1.ra between @ra - @r and @ra + @r -- quick filter on ra and o1.dec between @dec-@r and @dec+@r -- quick filter on dec and ( (sqrt( power(o1.cx-@cx,2)+power(o1.cy-@cy,2)+power(o1.cz-@cz,2))))

< @r -- careful filter on distance

Eliminates the ~ 21% = 1-π/4False positives

Bounding box

Summary

• SQL is a set oriented language

• You can express constraints as rows

• Then You – Can evaluate LOTS of predicates per second– Can do set algebra on the predicates.

• Benefits from SQL parallelism

• SQL == Prolog?