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1 Designing for 20TB Disk Drives And enterprise storage Jim Gray, Microsoft research.

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1 1 Designing for 20TB Disk Drives And enterprise storage Jim Gray, Microsoft research

2 2 Disk Evolution Capacity:100x in 10 years 1 TB 3.5 drive in 2005 20 TB? in 2012?! System on a chip High-speed SAN Disk replacing tape Disk is super computer ! Kilo Mega Giga Tera Peta Exa Zetta Yotta

3 3 Disks are becoming computers Smart drives Camera with micro-drive Replay / Tivo / Ultimate TV Phone with micro-drive MP3 players Tablet Xbox Many more… Disk Ctlr + 1Ghz cpu+ 1GB RAM Comm: Infiniband, Ethernet, radio… Applications Web, DBMS, Files OS

4 4 Intermediate Step: Shared Logic Brick with 8-12 disk drives 200 mips/arm (or more) 2xGbpsEthernet General purpose OS 10k$/TB to 100k$/TB Shared Sheet metal Power Support/Config Security Network ports These bricks could run applications (e.g. SQL or Mail or..) Snap ~1TB 12x80GB NAS NetApp ~.5TB 8x70GB NAS Maxstor ~2TB 12x160GB NAS IBM TotalStorage ~360GB 10x36GB NAS

5 5 Hardware Homogenous machines leads to quick response through reallocation HP desktop machines, 320MB RAM, 3u high, 4 100GB IDE Drives $4k/TB (street), 2.5processors/TB, 1GB RAM/TB 3 weeks from ordering to operational Slide courtesy of Brewster Kahle, @

6 6 Disk as Tape Tape is unreliable, specialized, slow, low density, not improving fast, and expensive Using removable hard drives to replace tapes function has been successful When a tape is needed, the drive is put in a machine and it is online. No need to copy from tape before it is used. Portable, durable, fast, media cost = raw tapes, dense. Unknown longevity: suspected good. Slide courtesy of Brewster Kahle, @

7 7 Disk As Tape: What format? Today I send NTFS/SQL disks. But that is not a good format for Linux. Solution: Ship NFS/CIFS/ODBC servers (not disks) Plug disk into LAN. DHCP then file or DB server via standard interface. Web Service in long term

8 8 State is Expensive Stateless clones are easy to manage App servers are middle tier Cost goes to zero with Moores law. One admin per 1,000 clones. Good story about scaleout. Stateful servers are expensive to manage 1TB to 100TB per admin Storage cost is going to zero(2k$ to 200k$). Cost of storage is management cost

9 9 Databases (== SQL) VLDB survey (Winter Corp). 10 TB to 100TB DBs. Size doubling yearly Riding disk Moores law 10,000 disks at 18GB is 100TB cooked. Mostly DSS and data warehouses. Some media managers

10 10 Interesting facts No DBMSs beyond 100TB. Most bytes are in files. The web is file centric eMail is file centric. Science (and batch) is file centric. But…. SQL performance is better than CIFS/NFS.. CISC vs RISC

11 11 BarBar: the biggest DB 500 TB Uses Objectivity SLAC events Linux cluster scans DB looking for patterns

12 12 300 TB (cooked) Hotmail / Yahoo Clone front ends ~10,000@hotmail. Application servers ~100 @ hotmail Get mail box Get/put mail Disk bound ~30,000 disks ~ 20 admins

13 13 AOL (msn) (1PB?) 10 B transactions per day (10% of that) Huge storage Huge traffic Lots of eye candy DB used for security/accounting. GUESS AOL is a petabyte (40M x 10MB = 400 x 10 12 )

14 14 Google 1.5PB as of last spring 8,000 no-name PCs Each 1/3U, 2 x 80 GB disk, 2 cpu 256MB ram 1.4 PB online. 2 TB ram online 8 TeraOps Slice-price is 1K$ so 8M$. 15 admins (!) (== 1/100TB).

15 15 Astronomy Ive been trying to apply DB to astronomy Today they are at 10TB per data set Heading for Petabytes Using Objectivity Trying SQL (talk to me offline)

16 16 Scale Out: Buy Computing by the Slice 709,202 tpmC! == 1 Billion transactions/day Slice: 8cpu, 8GB, 100 disks (=1.8TB) 20ktpmC per slice, ~300k$/slice clients and 4 DTC nodes not shown

17 17 ScaleUp: A Very Big System! UNISYS Windows 2000 Data Center Limited Edition 32 cpus on 32 GB of RAM and 1,061 disks (15.5 TB) Will be helped by 64bit addressing 24 fiber channel

18 18 Hardware SQL\Inst1 SQL\Inst2 SQL\Inst3 Spare F G L KPQE E JJ O O I H M N R S 2200 2200 2200 2200 2200 2200 2200 2200 2200 One SQL database per rack Each rack contains 4.5 tb 261 total drives / 13.7 TB total Meta Data Meta Data Stored on 101 GB Fast, Small Disks (18 x 18.2 GB) Imagery Data Imagery Data Stored on 4 339 GB Slow, Big Disks (15 x 73.8 GB) To Add 90 72.8 GB Disks in Feb 2001 to create 18 TB SAN 8 Compaq DL360 Photon Web Servers Fiber SAN Switches 4 Compaq ProLiant 8500 Db Servers

19 19 Amdahls Balance Laws parallelism law: If a computation has a serial part S and a parallel component P, then the maximum speedup is (S+P)/S. balanced system law: A system needs a bit of IO per second per instruction per second: about 8 MIPS per MBps. memory law: = 1: the MB/MIPS ratio (called alpha ( )), in a balanced system is 1. IO law: Programs do one IO per 50,000 instructions.

20 20 Amdahls Laws Valid 35 Years Later? Parallelism law is algebra: so SURE! Balanced system laws? Look at tpc results (tpcC, tpcH) at Some imagination needed: Whats an instruction (CPI varies from 1-3)? RISC, CISC, VLIW, … clocks per instruction,… Whats an I/O?

21 21 Disks / cpu 50 22 TPC systems Normalize for CPI (clocks per instruction) TPC-C has about 7 ins/byte of IO TPC-H has 3 ins/byte of IO TPC-H needs ½ as many disks, sequential vs random Both use 9GB 10 krpm disks (need arms, not bytes) MHz/ cpu CPImips KB / IO IO/s / disk Disk s MB/s / cpu Ins/ IO Byte Amdahl 1 116 8 TPC-C= random 5502.1262810039740 7 TPC-H= sequential 5501.245864100176141 3

22 22 TPC systems: Whats alpha (=MB/MIPS ) ? Hard to say: Intel 32 bit addressing (= 4GB limit). Known CPI. IBM, HP, Sun have 64 GB limit. Unknown CPI. Look at both, guess CPI for IBM, HP, Sun Alpha is between 1 and 6 MipsMemory Alpha Amdahl11 1 tpcC Intel8x262 = 2Gips4GB 2 tpcH Intel8x458 = 4Gips4GB 1 tpcC IBM24 cpus ?= 12 Gips64GB 6 tpcH HP32 cpus ?= 16 Gips32 GB 2

23 23 Performance (on current SDSS data) Run times: on 15k$ COMPAQ Server (2 cpu, 1 GB, 8 disk) Some take 10 minutes Some take 1 minute Median ~ 22 sec. Ghz processors are fast! (10 mips/IO, 200 ins/byte) 2.5 m rec/s/cpu ~1,000 IO/cpu sec ~ 64 MB IO/cpu sec

24 24 How much storage do we need? Soon everything can be recorded and indexed Most bytes will never be seen by humans. Data summarization, trend detection anomaly detection are key technologies See Mike Lesk: How much information is there: See Lyman & Varian: How much information Yotta Zetta Exa Peta Tera Giga Mega Kilo A Book.Movi e All LoC books (words) All Books MultiMedia Everything ! Recorded A Photo 24 Yecto, 21 zepto, 18 atto, 15 femto, 12 pico, 9 nano, 6 micro, 3 milli

25 25 Standard Storage Metrics Capacity: RAM: MB and $/MB: today at 512MB and 200$/GB Disk:GB and $/GB: today at 80GB and 70k$/TB Tape: TB and $/TB: today at 40GB and 10k$/TB (nearline) Access time (latency) RAM: 100 ns Disk: 15 ms Tape: 30 second pick, 30 second position Transfer rate RAM: 1-10 GB/s Disk: 10-50 MB/s - - -Arrays can go to 10GB/s Tape: 5-15 MB/s - - - Arrays can go to 1GB/s

26 26 New Storage Metrics: Kaps, Maps, SCAN Kaps: How many kilobyte objects served per second The file server, transaction processing metric This is the OLD metric. Maps: How many megabyte objects served per sec The Multi-Media metric SCAN: How long to scan all the data the data mining and utility metric And Kaps/$, Maps/$, TBscan/$

27 27 More Kaps and Kaps/$ but…. Disk accesses got much less expensive Better disks Cheaper disks! But: disk arms are expensive the scarce resource 1 hour Scan vs 5 minutes in 1990 100 GB 30 MB/s

28 28 Data on Disk Can Move to RAM in 10 years 100:1 10 years

29 29 The Absurd 10x (=4 year) Disk 2.5 hr scan time (poor sequential access) 1 aps / 5 GB (VERY cold data) Its a tape! 1 TB 100 MB/s 200 Kaps

30 30 Its Hard to Archive a Petabyte It takes a LONG time to restore it. At 1GBps it takes 12 days! Store it in two (or more) places online (on disk?). A geo-plex Scrub it continuously (look for errors) On failure, use other copy until failure repaired, refresh lost copy from safe copy. Can organize the two copies differently (e.g.: one by time, one by space)

31 31 Auto Manage Storage 1980 rule of thumb: A DataAdmin per 10GB, SysAdmin per mips 2000 rule of thumb A DataAdmin per 5TB SysAdmin per 100 clones (varies with app). Problem: 5TB is 50k$ today, 5k$ in a few years. Admin cost >> storage cost !!!! Challenge: Automate ALL storage admin tasks

32 32 How to cool disk data: Cache data in main memory See 5 minute rule later in presentation Fewer-larger transfers Larger pages (512-> 8KB -> 256KB) Sequential rather than random access Random 8KB IO is 1.5 MBps Sequential IO is 30 MBps (20:1 ratio is growing) Raid1 (mirroring) rather than Raid5 (parity).

33 33 Data delivery costs 1$/GB today Rent for big customers: 300$/megabit per second per month Improved 3x in last 6 years (!). That translates to 1$/GB at each end. You can mail a 160 GB disk for 20$. Thats 16x cheaper If overnight its 4 MBps. 3x160 GB ~ ½ TB

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