Diggin' technology every day

March 6, 2013

New Seagate Hybrid disks coming!

Filed under: Storage — Tags: , — Nate @ 10:13 am

I first saw this yesterday over on El Reg, which seemed to have found a leaked url because at the time there was no mention of the drives elsewhere on the main Seagate site. A short time ago I came across another article via Slashdot, which mentions one major thing that yesterday’s article missed: SSD accelerated write caching.

We spoke with product manager David Burks this afternoon and have new details to report, including the revelation that the latest version of the Adaptive Memory caching technology has the ability to cache some host writes.


This new, dual-mode NAND is apparently faster than the SLC flash used in the old Momentus XT.

Though I find it interesting that they do force cached writes to the spinning rust in the event of power loss, instead of letting it sit in flash to be written the next time the drive is powered up.

Experience with Momentus XT

I have been a fan of the Momentus XT for a while now, I put one in my main laptop 1-2 years ago, upgraded from the original 320GB Hitachi 7200RPM disk that it came with (Toshiba laptop carrying an Hitachi drive?? seemed strange to me), to the original 500GB XT.

The speed up was significant – even though my laptop has 8GB of memory and really never goes above 40-50% memory usage, so always I have at least 4GB available as disk buffers — the acceleration the SSD provided was very noticeable.  Though it left me wanting more … I have thought on many occasions whether or not to go full SSD – but I needed/wanted something that had a lot of space, the laptop is dual boot and I have VM images as well. With the ability to hold only a single disk internally hybrid has been the best option.

I just wish it had more flash – I’d be happy to pay much more if it had say 32GB of flash on board, instead of the 4GB that it currently has.

A few months ago I decided to upgrade my desktop at work with a pair of Momentus 750GB drives, which each have 8GB of flash on board. That system is not dual boot but does run a Windows VM 24/7 for things I need windows for (the main OS is Ubuntu 10.04 – same as my laptop). I felt that separating the I/O for the VM(s — occasionally I run other VMs for testing things locally) would be good – also isolating the flash cache so windows has it’s own and Linux gets it’s own was good too — and hell the drives were cheap.  That system has 16GB of memory so even more room for buffers – the acceleration there was even more dramatic. I had never seen Linux go from command line to X windows login screen(GDM) in a (small) fraction of a second. But it did after the cache was warmed up (significantly faster than the XT on my laptop).

The 750GB variant has four advantages over my 500GB:

  • 6G SATA (didn’t matter to me all my systems are 3G)
  • 8GB cache (double what the 500GB has)
  • “Flash Management” – whatever that is
  • “Fast Boot technology” – whatever that is

So a few weeks ago I went and bought a 750GB XT for my laptop (haven’t installed it yet), and here we have the new stuff coming out!

New 2.5″ hybrids vs old XT

There are some significant advantages of these new hybrids –

  • 1TB vs 750GB
  • $99 vs $159 (Newegg – I bought mine online at Best buy for ~$139, picked up same day!)
  • Ability to cache some writes vs. no write caching at all
  • 64MB cache vs 32MB

I did see one potentially big disadvantage of the new hybrids – power usage.  The power draw while seeking on the new hybrids(2.7W) is more than double that of the Momentus XT (1.3W). Power draw for idle is actually 0.2W less than on the XT. I wonder what drives the power usage so much higher ? Maybe it is a typo in the data sheet.

The article above reports that Seagate says there is backup power to flush the write buffers in the event of sudden power loss, a problem that seems wide spread amongst SSDs in general. Myself I had a Corsair SSD corrupt itself a little bit a few years ago when it was connected to a system with a UPS that had a dead battery. The UPS did a self test – which then cut the power to the system because the battery was dead, and the file system became corrupt. I don’t recall how I recovered the system but I think I managed to without re-installing. I thought the problem was fairly isolated to my cheap crap SSD, so was interested to learn the problem is much more wide spread covering large sectors of the market and persists even today.

Seagate of course recently announced they were discontinuing non hybrid 7200RPM laptop drives. Which is a fine idea — when you can get a 1TB hybrid drive for only $99 that’s a pretty amazing price point, even over their existing XT series.

I suspect that especially with the new price point it will cause people to think harder on whether or not they want to go full SSD on their laptops or not.

Availability of the new 2.5″ hybrids are expected in the next week or so.

New 3.5″ Desktop Hybrids

Finally there are desktop hybrids as well, which appear to be identical other than in a larger form factor, and offering a 2TB model. Prices here were reported as $99 for 1TB and $149 for 2TB.

I do have one workstation at home which I setup for some gaming about a year ago, though recently have not been using it, in it is a 750GB Momentus XT along with a few other drives – including a low end cheap 64GB Corsair SSD that I bought a few years ago. I configured Windows 7 to use that SSD as a cache(using Ready Boost – I think that is what it is called) — though have not seen any noticeable performance boost – which surprised me quite a bit(especially given the size of the SSD). I thought it would be caching the data from the games and stuff but load times still seemed relatively normal.

Availability of these 3.5″ hybrids is expected late next month.


I think I will hold onto the 750GB XT I just bought, and not return it. I don’t feel comfortable returning it just because something newer/better might be coming out. Doesn’t seem right. I’ll find a use for it somewhere.. I don’t know yet if I will upgrade my laptop with that disk, or buy the 1TB new stuff. I’ll be very interested to see the benchmarks of the new drives vs the old ones. Seagate claims the MLC is faster than the SLC used in the XT. Power draw isn’t too much of a consideration my laptop doesn’t run more than about 2.5 hours anyway(also my laptop spends 99% of it’s time plugged in), I’m not sure how much doubling the power draw on the disk(only during seeks) would have on that number.

I have read Western Digital is coming out with hybrid drives too – I wonder if they will up the ante by offering a premium model with more cache on it, I can hope at least. I’d love to see 32 or even 64GB cache in a 2.5″ form factor.

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