Last week, in my posting on Toshiba's latest 1.8" drive
, Robert Pearson asks:
You may not be the right person to ask but I am asking everyone so "How do you see hybrid disk drives?"
(For the record, I am not immediately related to Robert. At onepoint, "Pearson" was the 12th most common surname in the USA, but now doesn't even make the Top 100.)
Robert, I would like to encourage you and everyone else to ask questions, don't worry if I am the wrong person to ask, asprobably I know the right person within IBM. Some people have called me the "Kevin Bacon" of Storage,as I am often less than six degrees away from the right person, having worked in IBM Storage for over 20 years.
For those not familiar with hybrid drives, there is a good write-up in Wikipedia.
Unfortunately, most of the people I would consult on this question, such as those from Market Intelligence or Research, are on vacation for the holidays, so, Robert, I will have to rely on my trusted 78-card Tarot deck and answer you with a five-card throw.
- Your first card, Robert, is the Hermit. This card represents "introspection". The best I/O is no I/O, which means that if applications can keep the information they need inside server memory, you can avoid the bus bandwidth limitations to going to external storage devices. Where external storage makes sense is when data is shared between servers, or when the single server is limited to a set amount of internal memory. So, consider maxing out the memory in your server first (IBM would be glad to sell you more internal memory!!!), then consider outside solid-state or hybrid devices. Windows for example has an architectural limit of 4GB.
- Your second card, Robert, is the Four of Cups, representing "apathy".On the card, you see three cups together, with the fourth cup being delivered from a cloud. This reminds me thatwe have three storage tiers already (memory,disk,tape), and introducing a fourth tier into the mix may not garnermuch excitement. For the mainframe, IBM introduced a Solid-State Device, call the Coupling Facility, which can be accessed from multipleSystem z servers. It is used heavily by DFSMS and DB2 to hold shared information. However, given some customer's apathytowards Information Lifecycle Management which includes "tiered storage", introducing yet another tier that forcespeople to decide what data goes where may be another challenge.
- Your third card, Robert, is the Chariot, which represents "Speed, Determination,and Will". In some cases, solid state disk are faster for reading, but can be slower for writing. In the case of ahybrid drive, where the memory acts as a front-end cache, read-hits would be faster, but read-misses might be slower.While the idea of stopping the drives during inactivity will reduce power consumption, spinning up and slowing downthe disk may incur additional performance penalties. At the time of this post, the fastest disk system remains the IBM SAN Volume Controller, based on SPC-1 and SPC-2 benchmarks in excess of those published for other devices.
- Your fourth card, Robert, is the Eight of Pentacles, which represents"Diligence, Hard work". The pentacles are coins with five-sided stars on them, and this often represents money.Our research team has projected that spinning disk will continue to be a viable and profitable storage media for at least anothereight years.
- Your fifth and last card, Robert, is the World, which normallyrepresents "Accomplishment", but since it is turned upside down, the meaning is reversed to "Limitation". Some Hybriddisks, and some types of solid state memory in general, do have limitations in the number of write cycles they can handle. For thoseunhappy with the frequency and slowness for rebuilds on SATA disk may find similar problems with hybrid drives.For that reason, businesses may not trust using hybrid drives for their busiest, mission-critical applications, but certainlymight use it for archive data with lower write-cycle requirements.
The tarot cards are never wrong, but certainly interpretations of the cards can be.
technorati tags: Robert Pearson, Kevin Bacon, IBM, storage, Tarot, card, deck, Hermit, Four-of-Cups, Coupling Facility, Chariot, SAN Volume Controller, SVC, SPC-1, SPC-2, benchmarks, Texas Memory Systems, Eight-of-Pentacles, World, Hybrid, SATA