Question about Hybrid disks

[Ponch]

As most of you know, Seagate makes hybrid disks since a few years, and they seem quite good value. But I haven't found much info about how you actually see the disk. For instance for a 750Gig disk with 8Gig of SSD, I read someone's comment that you are not able to install Windows 7 in the SSD part. He doesn't say why. Seagate says the integration of SSD technology is "transparent" so I guess you don't really see the SSD but the disk (device) uses it internally.

Also If I get it right, if you make a dual boot on 2 separate system partitions, you can't "attribute" half the SSD to each so either only one of your OS is gaining from the nature of the disk or you loose a bit of advantage every time you switch from one OS to the other as the internal organisation has to recompute the optimisation ?

Or do I get it completely wrong? Has anyone got a little experience/info on those hybrid disks to share ? Thanks.

Edited March 23, 2013 by Ponch

[jaclaz]

They are (supposedly) "smart" drives.

They learn by experience .

The most used/needed files will little by little become resident on the SSD part (actually a copy of them).

See:

http://www.mydefrag.com/forum/index.php?topic=3958.0

Dual boot is "pure folly" on these disk drives (the disk will need some time to re-learn usage, and as soon as it does, you will allready be booting the "other" OS and the poor little controller needs to start again from square #1 ).

The SSD parts works exclusively as a cache, basically the most used files (that ANYWAY reside on hard disk) are copied to the SSD and when a file is required by the OS, there is a sort of look-up table and if a copy of the file is found on the SSD that file is "served" instead of the one on HD.

You have NO control whatsoever on what happens inside the thingy. (this is what "transparent" means, "completely obfuscated" )

jaclaz

[Ponch]

"Pure folie" (it's french) ... I thought so. Thanks.

[MagicAndre1981]

Intel has a technology which is called "Intel Smart Response" which allows you to use a small SSD as cache:

http://superuser.com/questions/568674/why-is-my-hybrid-disk-not-active/568719#568719

[CharlotteTheHarlot]

The SSD parts works exclusively as a cache, basically the most used files (that ANYWAY reside on hard disk) are copied to the SSD and when a file is required by the OS, there is a sort of look-up table and if a copy of the file is found on the SSD that file is "served" instead of the one on HD.

You have NO control whatsoever on what happens inside the thingy. (this is what "transparent" means, "completely obfuscated" )

I thought about getting a few of these, the Momentus models from Seagate for use as system disks, but am not convinced of the value. I remember reading this ( among many other ) direct comparisons ...

Comparing Mechanical, Solid-State, And Hybrid Storage ( Tom's Hardware 2012-06-15 )

The three drives there, top to bottom, are ...

Platters ... Western Digital Raptor X ... 150 GB ... SATA 1.5 Gb/s ... 16 MB Cache ... 10,000 RPM

Hybrid ..... Seagate Momentus XT ........ 750 GB ... SATA 6.0 Gb/s ... 32 MB Cache .... 7,200 RPM

SSD ........ Samsung 830 ................. 64 GB ... SATA 6.0 Gb/s

There is definitely a performance gain to be had at bootup. In most comparisons I have seen, the hybrids come much closer to SSD results than normal hard drives with platters. I would imagine that after the cache "gets educated" ( it learns like any other caching algorithm ) things like game loading might improve also when the resources get mirrored to the SSD. I cannot see how a hybrid will ever help for typical work, like editing large files, videos, music, etc, because all the gains will be counter-balanced at some point when the mirrored file gets written back to the platters. This must happen eventually because it wouldn't seem to be logical for some files only to exist on the SSD as this defeats the purpose of a hybrid using a relatively small cache space. Why not just get a full blown SSD instead? I imagine the algorithm rejects very large files anyway. I may just not be understanding the concept yet. I suppose the procedure could be for all files to be first written to the SSD cache, and then as time goes on, using file access times as a key, write the least accessed data to the platters and vice versa, get the most accessed file from the platters onto the SSD.

But the main problem so far is still price. For about $100 USA you can easily get a 2TB traditional HDD, but that same money apparently can only get a 1/4 sized Momentus hybrid. Today at NewEgg ...

(4) Seagate Hybrid HDD's ...

$ 99.99 ... Seagate Solid State Hybrid ... 500 GB ... SSD Cache: 8GB ... Model ST500LM000 .... Item N82E16822178339 ... Bare Drive

$ 99.99 ... Seagate Momentus XT .......... 500 GB ... SSD Cache: 4GB ... Model STAN500100 .... Item N82E16822148704 ... Retail Kit

$129.99 ... Seagate Solid State Hybrid .. 1000 GB ... SSD Cache: 8GB ... Model ST1000LM014 ... Item N82E16822178340 ... Bare Drive

$159.99 ... Seagate Momentus XT .......... 750 GB ... SSD Cache: 8GB ... Model STBD750100 .... Item N82E16822148940 ... Retail Kit

(12) Assorted 2TB standard HDD's ...

$ 99.99 Toshiba DT01ACA200 2TB 7200 RPM SATA 6.0Gb/s 3.5" Bare Drive Cache: 64MB Model DT01ACA200 Item N82E16822149407 Free Shipping

$101.99 Toshiba DT01ACA DT01ACA200 2 TB 3.5" Cache: 64MB Model HDKPC09 Item N82E16822149434 $7.28 Shipping

$104.99 Western Digital WD Green WD20EARX 2TB SATA 6.0Gb/s 3.5" Bare Drive OEM Cache: 64MB Model WD20EARX Item N82E16822136891 Free Shipping

$104.99 Seagate Pipeline HD ST2000VM003 2 TB 3.5" SATA 3Gb/s Cache: 64MB Model ST2000VM003 Item N82E16822178271 $7.28 Shipping

$109.99 Western Digital WD Green WDBAAY0020HNC-NRSN 2TB SATA 3.0Gb/s 3.5" Retail kit Cache: 32MB Model WDBAAY0020HNC-NRSN Item N82E16822136772 Free Shipping

$109.99 Seagate SV35 Series ST2000VX000 2TB 7200 RPM SATA 6.0Gb/s 3.5" Bare Drive Cache: 64MB Model ST2000VX000 Item N82E16822148902 $4.99 Shipping

$109.99 Seagate Barracuda ST2000DM001 2TB 7200 RPM SATA 6.0Gb/s 3.5" Bare Drive Cache: 64MB Model ST2000DM001 Item N82E16822148834 Free Shipping

$109.99 Seagate Barracuda STBD2000101 2TB 7200 RPM SATA 6.0Gb/s 3.5" Retail kit Cache: 64MB Model STBD2000101 Item N82E16822148910 Free Shipping

$109.99 Western Digital WD AV-GP WD20EURS 2TB SATA 3.0Gb/s 3.5" Bare Drive OEM Cache: 64MB Model WD20EURS Item N82E16822136783 Free Shipping

$109.99 Western Digital WD Green WD20EZRX 2TB IntelliPower SATA 6.0Gb/s 3.5" Bare Drive Cache: 64MB Model WD20EZRX Item N82E16822236404 Free Shipping

$109.99 Toshiba PH3200U-1I72 2TB 7200 RPM SATA 6.0Gb/s 3.5" Retail Kit Cache: 64MB Model PH3200U-1I72 Item N82E16822149397 Free Shipping

$115.99 Seagate Barracuda ST320005N4A1AS-RK 2TB 5900 RPM SATA 3.0Gb/s 3.5" Retail kit Cache: 64MB Model ST320005N4A1AS-RK Item N82E16822148487 Free Shipping

Maybe it's just me, but I would still take the huge storage over the hybrid compromise.

Another problem IMHO is related to what Jaclaz said, since there apparently is no control over the SSD cache portion, how do you ensure that there is not any stale or unwanted data in the cache? I haven't been able to determine if there is a "sync" or "flush" style management command. For example, something I have worried about is if I get a computer that uses a hybrid for the system disk in here that is infected. So after running AV and malware tools against it how can you be assured that both copies of an infected file ( one on the disk platters and the other in the SSD cache ) are in fact cleaned or deleted? I hate ambiguity and failure vectors, especially when I cannot state something with certainty like "this system is clean".

I am working under the assumption that these hybrids have incredibly smart firmware that maintain a mirrored file index that is regularly sync'ed from platters to SSD, hopefully almost instantaneously, whenever an indexed file is altered. But if that is in fact the case, wouldn't it kinda defeat the purpose of the cache again? And why does this all now remind me of dirty bit flags and FAT free space count going out of sync periodically. I sure hope they have thought of all the pitfalls.

EDIT: updated image URL

Edited May 16, 2013 by CharlotteTheHarlot

[jaclaz]

... since there apparently is no control over the SSD cache portion, how do you ensure that there is not any stale or unwanted data in the cache?

JFYI:

http://www.forensicfocus.com/Forums/viewtopic/p=6562822/#6562822

The good guys @Tom's hardware made a nice spider graph:

http://www.tomshardware.com/reviews/momentus-xt-750gb-review,3223-7.html

BUT if you want "real" speed, you must pay for it, get a PCI-Express SSD drive!

jaclaz

[allen2]

Non Enterprise PCI-express SSD doesn't provide that much speed on incompressible data in comparison with Samsung ssd 840 PRO.

Also since i bought the Revodrive 3 X2 some month ago, i can tell i couldn't get it to provide the transfer rate even with highly compressible data and its bad side is that it doesn't offer linear speeds like an ssd should. I then tried the simple Revodrive 3 (same size) and it provided better performance especially for incompressible data except for high i/o usages. But both are only 20% faster than the speed from Samsung SSD 840 PRO (on the paper as i currently didn't had the chance to try the 840 PRO).

As a side note, the Revodrive 3 x2 heated a lot more than the Revodrive 3 and both of them heat more than any sata ssd i ever tried.