1

CS 294-42: Technology Trends

Ion Stoica (http://www.cs.berkeley.edu/~istoica/classes/cs294/11/)

September 12, 2011

2

“Skate where the puck's going, not where it's been” – Walter Gretzky

Processors

MIMD (Multi-Core Processors) – linear increase: two additional cores every two years

SIMD (GPUs) – exponential increase: width double every four years

3

SSDs Performance:

Reads: 25us latency Write: 200us latency Erase: 1,5 ms

Steady state, when SSD full One erase every 64 or 128 reads (depending on page

size) Lifetime: 100,000-1 million writes per page

4

Rule of thumb: writes 10x more expensive than reads, and erases 10x more expensive than writes

Storage Performance & PriceBwdth (sequential R/W)

Cost/GB Size

HHD 50-100 MB/s $0.05-0.1/GB 2-4 TB

SSD1 200-500 MB/s (SATA)1.5 GB/s (PCI)

$2-4/GB 200GB-1TB

DRAM 10-16 GB/s $12-13/GB 64GB-256GB

5

Bwdth: SSD up to x10 than HDD, DRAM > x10 than SSDPrice: HDD x20 less than SSD, SSD x5 less than DRAM

1http://www.fastestssd.com/featured/ssd-rankings-the-fastest-solid-state-drives/

Storage Price Trends RAMs: x2 every ~20 month (http://www.jcmit.com/memoryprice.htm)

1990-2000: x75 decrease 2000-2010: x63 decrease

Disks: x2 decrease every ~2 years SSDs prices dropped faster than disk prices for

last 5 year(http://rogerluethy.wordpress.com/2010/12/07/price-trends-of-hdds-vs-ssds/) But decrease slightly less over last year

6Storage price halves every ~2 years

Hard Drives (25 years ago) IBM Personal Computer/AT (1986)

30 MB hard disk - $500 30-40ms seek time 0.7-1 MB/s (est.)

730-40sec to scan entire disk

Memory (today)

96 GB RAM - $650-800 (ECC RAM) Memory bus speed: 10-16 GB/s

8

6-10sec to scan entire memory!

Working Set: RAM Doubling Software (1995)

9

Working Set (Today)

When was the last time your experience trashing on your laptop?

Memory growing faster than application’s needs – conjecture

10

Today’s memory, yesterday’s disk!

Working Set – Datacenters % of jobs whose full inputs fit in memory (~1 week)

11

Memory (GB)

Facebook (% jobs)

Microsoft (% jobs)

Yahoo! (% jobs)

8 69 38 66

16 74 51 81

32 96 82 97.5

64 97 98 99.5

128 98.8 99.4 99.8

192 99.5 100 100

256 99.6 100 100Nearly all jobs’ inputs fitting in main memory in near future?

(Ganesh Ananthanarayanan)

(Random) Thoughts Today’s disks, yesterday’s tapes [John Ousterhout]

Today’s memory, yesterday’s disk? Or should be today’s SSDs, yesterday’s disks? SSDs not great for caches (due limited writes) Perfect for archival though and GFS-like filer systems ;-)

In-memory computation not enough for interactive workloads Parallelism only way out if need to touch a lot of data

12

(Random) Thoughts (cont’d) Today’s servers in Hadoop clusters: 10-12 disks

Up to 1GB/s bwdth How to take advantage of this?

GPU use will only increase: faster increase in processing power than CPUs Need better support for virtualization What to do about memory bwdth?

For data intensive apps, locality will continue to be critical

13

Predictions??

Memory the new disk Working sets of more and more apps will fit in memory

SSDs will become the new tape (archival)

GPUs: main driver for increasing processing power Will be integrated in the main processor

14