Feeds

Flash and the five-minute rule

NAND then there was disruption

Remote control for virtualized desktops

Enter Flash

Enter the flash dragon. It's less expensive, generally speaking, than disk drives were in 1987 and this changes things. Flash is the disruptive technology that brings this RI discontinuity back into balance - that was the substance of Dale's SNIA pitch.

It has 100 times better IOPS per dollar and a thousand times better IOPS per milliwatt than disk at random reads. It is 10 times better at bandwidth per milliwatt than disk. It is also 10 times better at MB per milliwatt than DRAM, and wins big in the latency stakes over disk, but DRAM is better still.

Notwithstanding that disks are really good at doing sequential writes, flash not really buying you anything with writes, flash will show up as a disk and a DRAM replacement.

Dale provided five-minute rule RI numbers for flash against DRAM.  A slide stated: "Assuming that he cost of cache is dominated by its capacity, and the cost of backing store is dominated by its access cost (cost per IOPS), then the break even interval for keeping a page of data in cache is given by dividing the backing store cost per IOPS by the cache cost per page."

In 1987, using these metrics, disk cost $2,000/IOPS and RAM was $5/KB. A 1KB page's break-even point was 400 seconds.

In 2008, Dale said, disk was $1 per IOPS, a 2,000x reduction, and DRAM was $50/GB, a 100,000x reduction, meaning it was $0.05/MB. The 50KB page break-even was five minutes, the 4KB once was one hour and the 1KB one was five hours. There needed to be a 50-fold increase in page size to cache for break-even at five minutes.

Looking at break even for flash and hard drives (HDD)  in 2010 he said HDDS cost $1/IOPS, single-level cell (SLC) flash around $10/GB and multi-level cell (MLC) around $4/GB. A250KB page break even with SLC was five minutes, but five hours with a 4KB page size. It was five minutes with a 625KB page size with MLC flash and 13 hours with a 4KB MLC page size.

Again there needed to be a 50-fold increase in page size to cache for break even at five minutes.

Looking at DRAM and flash his numbers were $0.05/IOPS for 4KB enterprise SLC, $0.02 for 4KB and enterprise MLC, with DRAM at $20/GB. A 6KB page size SLC break even came out at five minutes, as did a 2KB page size MLC.

What does this mean?

Flash makes it cost-effective to keep more small random data in a NAND cache than DRAM, say a five-plus hour working set in NAND and a one-hour one in DRAM. The random data working set size in DRAM can be reduced.

Secure remote control for conventional and virtual desktops

Next page: Why Now?

More from The Register

next story
NSA SOURCE CODE LEAK: Information slurp tools to appear online
Now you can run your own intelligence agency
Azure TITSUP caused by INFINITE LOOP
Fat fingered geo-block kept Aussies in the dark
Yahoo! blames! MONSTER! email! OUTAGE! on! CUT! CABLE! bungle!
Weekend woe for BT as telco struggles to restore service
Cloud unicorns are extinct so DiData cloud mess was YOUR fault
Applications need to be built to handle TITSUP incidents
Stop the IoT revolution! We need to figure out packet sizes first
Researchers test 802.15.4 and find we know nuh-think! about large scale sensor network ops
Turnbull should spare us all airline-magazine-grade cloud hype
Box-hugger is not a dirty word, Minister. Box-huggers make the cloud WORK
SanDisk vows: We'll have a 16TB SSD WHOPPER by 2016
Flash WORM has a serious use for archived photos and videos
Astro-boffins start opening universe simulation data
Got a supercomputer? Want to simulate a universe? Here you go
Microsoft adds video offering to Office 365. Oh NOES, you'll need Adobe Flash
Lovely presentations... but not on your Flash-hating mobe
prev story

Whitepapers

Designing and building an open ITOA architecture
Learn about a new IT data taxonomy defined by the four data sources of IT visibility: wire, machine, agent, and synthetic data sets.
Getting started with customer-focused identity management
Learn why identity is a fundamental requirement to digital growth, and how without it there is no way to identify and engage customers in a meaningful way.
10 threats to successful enterprise endpoint backup
10 threats to a successful backup including issues with BYOD, slow backups and ineffective security.
Reg Reader Research: SaaS based Email and Office Productivity Tools
Read this Reg reader report which provides advice and guidance for SMBs towards the use of SaaS based email and Office productivity tools.
10 ways wire data helps conquer IT complexity
IT teams can automatically detect problems across the IT environment, spot data theft, select unique pieces of transaction payloads to send to a data source, and more.