WD Blue 4TB SSHD

[VirtualLarry]

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=9777767&Sku=

Looks like WD is re-purposing their "Blue" brand to some new SSHDs! Bigger than 1TB too!

 

[cbn]

Thanks for posting. I totally forgot about these type of drives.

Here is a review at StorageReview:

http://www.storagereview.com/wd_blue_sshd_4tb_review

(It beats the 4TB Seagate SSHD in the Storagemark 2010 HTPC Disk Capture benchmark, but loses in the others. Both 4TB SSHD have 8GB MLC NAND flash.)

Here is the back of the PCB showing the chips:

The Jmicron SSD controller is marked with JMF608u2.

JMF608 is a DRAM-less four channel SDD controller --> http://www.jmicron.com/product0102.html

 

[cbn]

There is also a WD Blue 1TB (also with 8GB MLC Nand) SSHD in 2.5" form factor:

http://www.newegg.com/Product/Product.aspx?Item=N82E16822236984


Here is the review from storage review:

http://www.storagereview.com/wd_blue_sshd_1tb_review

Here is a shot of the PCB (showing the DRAM-less Jmicron JMF608 SSD controller):

 

[VirtualLarry]

Interesting. Thanks, cbn!

I kind of wish WD would make a 2TB Blue SSHD, like Seagate does. I view that as sort of the "sweet spot" for a boot drive. The reason being, is that 2TB is the max that MBR drives can be, such that a 2TB SSHD would work for a boot drive in both a BIOS as well as a UEFI PC.

And the 4TB model, seems slightly overkill for both a boot drive (size-wise) and a storage drive (price-wise).

Just seems a bit out of place.

 

[cbn]

I kind of wish WD would make a 2TB Blue SSHD, like Seagate does. I view that as sort of the "sweet spot" for a boot drive. The reason being, is that 2TB is the max that MBR drives can be, such that a 2TB SSHD would work for a boot drive in both a BIOS as well as a UEFI PC.

2TB is a good target.

I would even be interested in a 1.2TB (single platter) 3.5" SSHD if they could get the price down so it wasn't that much more expensive compared to another single platter HDD.

With that mentioned, WD and Seagate must be feeling the heat from dropping SSD prices. And putting flash on 1TB or 1.2TB 3.5" hard drives will only close that gap faster. Maybe this even why WD went with the WD Black2 dual drive (which is a 120GB SSD plus 1TB HDD separately in a 2.5" package) rather than NAND performing cache duty and thus not adding to total capacity.

In any event, I am hoping these upcoming two channel DRAM-less SSD controllers supporting TLC can help with the cost and performance of dedicated cache (whether it is 1TB, 1.2TB or a 2TB SSHD drive). Two channel, DRAM-less, TLC replacing four channel, DRAM-less, MLC has to got to help.

 

[VirtualLarry]

In any event, I am hoping these upcoming two channel DRAM-less SSD controllers supporting TLC can help with the cost and performance of dedicated cache (whether it is 1TB, 1.2TB or a 2TB SSHD drive). Two channel, DRAM-less, TLC replacing four channel, DRAM-less, MLC has to got to help.

Hmm, considering that the NAND cache on SSHDs gets re-written often (I would imagine?), then I would probably want a drive that stuck to MLC for cache purposes, rather than TLC. With the small amount of NAND involved in an SSHD NAND cache, versus a full-blown SSD, and the reliability concerns with a small number of P/E cycles (500?), I really don't see using TLC for that purpose would have much of a cost savings.

Don't forget that one aspect in reliability of TLC SSDs, is the total number of cells, to spread out the writes to. You lose that reliability aspect with the small amount of NAND cache on an SSHD. (Unless, possibly, they OP by 100%, putting 16GB of actual TLC NAND onboard. But then it becomes more of an economic question than an engineering one - which offers better reliability - 8GB of 1000 P/E MLC NAND, or 16GB of 500 P/E TLC NAND?)

 

[cbn]

Hmm, considering that the NAND cache on SSHDs gets re-written often (I would imagine?)

According to this Article on Seagate Momentus XT the NAND doesn't get written too very often:

http://www.anandtech.com/show/3734/seagates-momentus-xt-review-finally-a-good-hybrid-hdd

The size of the NAND was a shocker to me when I first heard it. I honestly expected something much larger. In the Momentus XT however, the SLC NAND acts exclusively as a read cache - writes never touch the NAND. The drive looks at access patterns over time (most likely via a history table of LBAs and their frequency of access) and pulls some data into the NAND. If a read request comes in for an LBA that is present in the NAND, it's serviced out of the 4GB chip. If the LBA isn't present in the NAND, the data comes from the platters.

So I have been wondering if this same type of caching is used in the newer drives.

 

[cbn]

But then it becomes more of an economic question than an engineering one - which offers better reliability - 8GB of 1000 P/E MLC NAND, or 16GB of 500 P/E TLC NAND?)

For a scenario where a small amount of NAND is receiving a lot of writes, Apparently the controller design and its error correction plays a large role in extending the life of the flash:

http://forums.anandtech.com/showpost.php?p=37631339&postcount=3

But NAND flash memory has a weakness: the memory cells deteriorate slightly with each program/erase (P/E) or write/delete cycle. As each individual cell deteriorates, its ability to accurately hold a given charge state diminishes, causing its read error rate to increase. At some point (after too many P/E cycles), the errors can no longer be corrected, making the cell unusable.

The stronger the error correction, therefore, the longer the usable life of the flash memory cells. In other words, a really strong ECC technology enables cells to become substantially “weaker” and still be read reliably.

A more powerful error correction technology that withstands a higher raw bit error rate would let the cells deteriorate further – that is, would enable more P/E cycles on the NAND flash memory.

So I am thinking that scenario you described could be in the favor of TLC if there was a substantial difference in the quality of the controllers.

 

[cbn]

Virtual Larry,

Regarding 8GB MLC vs. 16GB TLC I found the following P/E cycle quotes:

http://www.anandtech.com/show/5067/understanding-tlc-nand/2

2Xnm planar MLC: 3000 P/E cycles
2Xnm planar TLC: 750 P/E cycles

So in that situation 8 GB MLC vs.16 GB TLC would favor MLC by 2:1 before any differences in controllers were factored in.

P.S. Samsung V-NAND TLC is rated at 2000 P/E cycles ---> http://anandtech.com/show/8747/samsung-ssd-850-evo-review/4

 

[AlienTech]

These drives cost $20-$30 more than ones without the nand on it. For that price they could have added 2-4bgb of ram which would show a far better performance improvement than the 64k memory they currently use.

Considering you can get 128k USB2 pen drives now for under $30 with speeds of 150mb's..Using one with ready cache would speed up everything. Or with 128GB SSD's under $40 now, just moving the super fetch and pre fetch and page files onto the SSD would show similar speeds. You could also use a portion of the SSD for ready cache.. NOT installing the OS on the SSD itself uses up only a small amount of ssd space. It would blow away any 8 or 16gb nand on the drive itself which only stores the most often accessed data, which is similar to what windows itself already does to an extent. But with that extra 90GB of space to speed up things much more.

If these drives were $5 to $10 difference it might be worth it but both seagate and wdc drives cost the same as getting a hard drive and an ssd individually.

 

[cbn]

These drives cost $20-$30 more than ones without the nand on it. For that price they could have added 2-4bgb of ram which would show a far better performance improvement than the 64k memory they currently use.

Considering you can get 128k USB2 pen drives now for under $30 with speeds of 150mb's..Using one with ready cache would speed up everything. Or with 128GB SSD's under $40 now, just moving the super fetch and pre fetch and page files onto the SSD would show similar speeds. You could also use a portion of the SSD for ready cache.. NOT installing the OS on the SSD itself uses up only a small amount of ssd space. It would blow away any 8 or 16gb nand on the drive itself which only stores the most often accessed data, which is similar to what windows itself already does to an extent. But with that extra 90GB of space to speed up things much more.

According to this thread, it would be possible to install Intel SRT and Operating system on the same SSD.

So for a 128GB SSD, 64GB could go for the OS and applications and 64 GB for cache (Alternatively 96GB could go for OS/applications and 32GB could be allocated to cache, etc.) Or with a 256GB SSD, 192GB could go for OS and applications and 64GB for cache.

Because larger drives are often times cheaper per GB than smaller drives, that would lower the price of the cache. For example with a $40 128GB SSD having 64GB dedicated to cache effectively makes that cost $20 (with 32GB allocated to cache the price comes out to be $10). On a larger 256GB drive if prices eventually drop to $60, the 64GB cache would effectively cost $15.

P.S. I did find out that wear leveling occurs below the level of the partitions. So lets say the 64GB cache partition receives a lot more writes (expected) than the OS/application partition....the wear would be evenly distributed across the SSD. Furthermore, I am thinking there would be other benefits to having 64GB cache on a larger drive rather than on a fully dedicated 64GB SSD.

 

[AlienTech]

There are lots of options if the nand is not on the drive itself. I still dont get why they only put such a small amount on the drive but charge so much. It just is not worth the extra cost. And yes with a 128GB drive you can put the entire OS on the SSD as well as a few programs and get SSD speeds.. I was only saying, buy a regular 4TB drive for $120 and spend $40 on a 128GB SSD instead of $170 for a SSHD... You would be far happier with it as long as you have a basic understanding of directories and drive letters etc.. In fact I use the soft and hard links to make a single drive appear to contain my SSD and hard drive data.. Even though some of the installed programs are on another drive but appear to be in the same drive as the OS install.. I even set up my hard drive to sleep after 20 minutes and it seems to be asleep most of the time as tv shows and such I watch are on the ssd and then moved later on to the hard drive. It might not be much but it keeps the room a little cooler with the hard drive powered down.. Power users can do the same thing but removing all the power saving features for higher speeds.. In fact they might see the most benefit from having 2 different drives..

heck when WDC first came out with this, they had an SSD card attached to the hard drive but appeared as a single drive and people were asking how to make it appear as separate drives.. But they were charging the same for a 32GB nand attachment as a 256GB SSD drive just because it was in a single case.