LSI 9265 MegaRAID Supplementary Review: The Beauty of CacheCade!

[The SSD Guy]

Today we are going to take an in-depth look at CacheCade, a new approach to storage systems that allows the perfect fusion of HDD capacity and SSD speed. With many large databases and enterprise users 'caught in the middle' with large HDD arrays, yet needing more performance from their existing infrastructure, CacheCade is a great option that allows the best of both worlds.

The concept behind CacheCade will be integrated into several consumer products by several big players in the computing industry, thus becoming very prevalent in the long term storage outlook. Both the enterprise and consumer segments are coming to grips with the changing landscape of storage brought about by the emergence of the SSD as the premium storage option. As always, the enterprise applications are trickling down into the consumer realm, and LSI is right at the forefront of development with this new method of storage enhancement.

CacheCade

CacheCade is a new technology that falls into a category of "Tiered Storage" that allows is for another 'Tier' of cache to be built upon a current HDD subsystem. Currently in a typical large enterprise server, you have RAID controllers connected to large mass arrays of HDD that serve data out to its 'customers'. There is a level of cache that is built into the controller, however, this amount of cache is very small. It is usually around 1GB, and rarely above 4 GB of RAM and mainly used to alleviate high write loads. On server arrays where the amount of data can go into hundreds of Terabytes, the 1-4GB of cache is rather inconsequential.

Enter the CacheCade theory which creates a supplemental layer of cache between the HDD and the controller. This cache can be much larger using SSDs that enjoy much lower access times and much higher random I/O speeds than HDD can ever hope to attain.

Lets start with an understanding of the advantages and disadvantages of each solution:



HDD Arrays

Pros

• Low Cost-When it comes to cost per GB, HDD reigns
• Usually involve existing infrastructure
• High storage capacity

Cons

• High power consumption
• High Latency (Slow)
• Large footprint
• Produce heat/need cooling

SSD Arrays

Pros

• Extreme speed compared to HDD
• Low latency
• Low power requirements
• Generate low amount of heat (negligible)
• Small footprint

Cons

• Price Per-GB is very high, especially for SLC drives
• Low capacity
• Endurance concerns

In the end, we have a complex mixture of factors here for companies to consider. If you already have a large system of HDD equipped servers, then you already have your infrastructure in place. Power, Cooling and Space are all very large concerns in these types of scenarios, however, if you are looking to speed up your systems to handle larger loads, you will need more of all three. More power, cooling and space will be required.

Switching to an all SSD or SAS HDD setup can be very cost prohibitive, and a very complex process, especially in scenarios where downtime is absolutely not tolerated. SSDs are much easier in terms of power, cooling and space, notwithstanding the fact that one SSD can do the work of several HDDs.

The key is to accelerate the performance of your existing HDD arrays without incurring the massive costs and investments that a total switch to SSD would require. That is exactly the concept behind CacheCade.

NEXT: Nuts and Bolts

Page 1- Introduction
Page 2- Nuts and Bolts
Page 3- Maximizing Benefits
Page 4- MLC vs SLC
Page 5- Test Bench and Protocol
Page 6- Single Zone Read
Page 7- Hot-Warm-Cool-Cold
Page 8- Conclusion

[FiftyOne]

very interesting. I'm wondering the enthusiast level applications for it all & setup/configuration.

[hpvd]

Thanks very much for you great review of cachecade!!

I've got two questions:

"The only negative aspect of CacheCade that I could gather is that each time the machine is rebooted; the caching has to begin anew."

are you very sure width this topic?
i found different information during my web research (german)
LSI MegaRAID CacheCade SSD Cache
"Der CacheCade Inhalt bleibt auch bei einem Reboot auf den SSDs erhalten."

perhaps there is a firmware option to activate this?

"More exciting, is that by the end of this year, LSI will be offering this solution with write-caching as well! This will truly be revolutionary, and we cannot wait to see the results."

sounds very exciting -
do you get this information directly from LSI? I couldn't find any further information on this in the web...

Best Regards
HPVD

[Computurd]

i have been in direct contact with the LSI team before the testing. It in fact doesnt retain the info upon reboot, i tested several times. they confirmed.
The information itself is still physically there, yet the Tables for accesing it are gone when you reboot. In several of their documents they mention it.
that will be one of the main differences with the usage when it switches to write caching, they will have to save the information for write data.
I hope that at that point they will switch the read caching to keep the data as well. not sure though.
write caching comes in Q3 for 9260 and controllers in that family, and 9265 in Q4 if memory serves correctly.


the lack of info/benchmarks from third parties was one reason we pursued this review with great interest.

there is room in the enthusiast "space" for this as well, for guys running home servers and such, this would be a great addition. Makes me think of the guys over at [H] who have 100+ TB servers, and do file sharing, torrents, etc from their homes. this would be perfect for that type of application. In enterprise usages, for small/medium/large companies, this is of course absolutely phenomenal as well.

[hpvd]

Many thanks for this fast and very detailed answer.
Sounds more than promising...
But why does it take so long until so Q4???

[Computurd]

yes it can be a bit of a wait until Q4 i am personally dying to upgrade to the socket 2011....god i cant wait, unfortunately its Q4 as well..

[FiftyOne]

lots of stuff coming in the later quarters, new intel chip coming out. theres talk it will be a 'tick-tock' update, which will be the first for some years & will include the 3d gate tech they've been spruking

[Computurd]

oh yes socket 2011 is the object of my desire...i lay awake at night thinking about it...imntegrated pcie 3.0 controller on-die, PCH functionality, 12 sata 6gb/s ports...pch direct connect....the intel IDF presentations on the storage subsystem entitled "next gen raid and sas" is enough to make my nerdy blood pound in my veins!!
i digress...
IDF 2010


gives you a clue where the onboards are heading. big thing for me is a clearer shot to the CPU for the PCIE bus....no more junk in the way, bye bye IOH you will NOT be missed!
bye bye NB...
great thing about that is latency latency latency, on the PCIE slots it should be superb. so you get exciting onboard raid capabilities and performance, plus some low latency runs direct to cpu for the pcie slots all wrapped in a uber 6 core chip....

[FiftyOne]

Agree with all of that. btw, you think the 3d gate tech will be carried through to things like the south bridge & all the other semi-conductor products (memory chips/south bridge etc) or will it be more the processor markets they will integrate the tech to (eg atom, celeron, i5 i7 etc)

[hpvd]

have you seen the 2308 chip?

seems to be the 2208 + pcie 3.0 + iops upgrade to 600.000
Does anyone can find more differences?

http://www.lsi.com/downloads/Public/...ct%20brief.pdf

Could not find the "pure" product brief of the 2208 only from the 9265 controller using this chip...