Seagate, Toshiba to Make SSD + HDD Hybrid?

We saw a quick and unceremonious demise to Microsoft’s ReadyBoost and ReadyDrive technology released at the dawn of the Vista era. Flash caches on the motherboard or worse yet, reusing a Flash memory stick as a disk cache never caught on. But now Seagate’s revisiting the idea of a hybrid hard drive by marrying an SSD and HDD into one logical disk. Is it as fast as an SSD? Is it cheaper than an SSD? Let’s take a look.


Seagate, Toshiba to Make SSD + HDD Hybrid?.

Some people may remember the poorly marketed and badly implemented Microsoft ReadyBoost technology hyped prior to the launch of Windows Vista. Microsoft’s intention was to speed throughput on machines without sufficient RAM memory to cache large parts of the Windows OS and shared libraries. By using a small Flash memory module on

Intel Turbo memory module for PCIe
Intel Turbo Memory to be used as ReadyDrive storage cache

the motherboard (Intel’s Turbo Memory) or by using a USB connected Flash memory stick one could create a Flash memory cache that would offset the effect of having 512MB or less RAM installed. In early testing done by folks like Anandtech and Tom’s Hardware system performance suffered terribly on computers with more than the 512MB of RAM targeted by Microsoft. By trying to use these techniques to offset the lack of RAM on computers with more than 512MB of RAM the computers ran slower using Vista. I had great hopes ReadyBoost at the time the flash cache method of speeding throughput on a desktop PC was heralding a new early of desktop PC performance. In the end it was all a myth created by the Microsoft marketing department.

Some time has passed since then Vista was released. RAM prices have slowly gone down. Even low end machines have more than adequate RAM installed to run Vista or now Windows 7 (no more machines with 512MB of RAM). The necessity of working around those limits of RAM is unnecessary. However total system level I/O has seen some gains through using somewhat expensive Flash based SSD (solid state disks). Really this is what we have all been waiting for all along. It’s flash memory modules like the ones Intel tried using for it’s  ReadyDrive capable Turbo Memory technology. However these were wired into a PCIe controller and optimized for fast I/O, faster than a real spinning hard disk. The advantage over the ReadyBoost was the speed of the PCIe interface connected to the Flash memory chips. Enterprise data centers have begun using some Flash SSDs as caches with some very high end product using all Flash SSDs in their storage arrays. The entry level price though can be daunting to say the least. 500GB SSD disks are the top of the line, premium priced products and not likely to be sold in large quantity until the prices come down.

Seagate is now offering a product that has a hybrid Flash cache and spinning disk all tied into one SATA disk controller.

Seagate hybrid hard drive
Seagate Momentus XT

The beauty of this design is the OS doesn’t enter into the fray. So it’s OS agnostic. Similarly the OS doesn’t try to be a disk controller. Seagate manages all the details on its side of the SATA controller and OS just sees what it thinks is a  hard disk that it sends read/write commands. In theory this sounds like a step up from simple spinning disks and maybe a step below a full flash based SSD. What is the performance of a hybrid drive like this?

As it turns out The Register did publish a follow-up with a quick benchmark (performed by Seagate) of the Seagate Moments XT compared to middle and top of the line spinning hard drives. The Seagate hybrid drive performs almost as well as an the Western Digital SSD included in the benchmark. That flash memory caches the stuff that needs quick access, and is able to refine what it stores over time based on what it is accessed most often by the OS. Your boot times speed up, file read/write times speed up all as a result of the internal controller on the hybrid drive. The availability if you check Amazon’s website is 1-2months which means you and I cannot yet purchase this item. But it’s encourage and I would like to see some more innovation in this product category. No doubt lots of optimization and algorithms can be tried out to balance the Flash memory and spinning hard disks. I say this because of the static ram cache that’s built into the Momentus XT which is 32MBytes in size. Decide when data goes in and out, which cache it uses (RAM or Flash) and when it finally gets written to disk is one of those difficult Computer Science type optimization problems. And there are likely as many answers as there are Computer Scientists to compute the problem. There will be lots of room to innovate if this product segment takes hold.

Author: carpetbomberz

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