Replacing system drive

[Alek Trishan]

I'm looking to replace my system drive (C) in a Windows 7 computer. It's
a 120GB SSD and I'm wondering whether I should just get another SSD or a
hybrid drive.

Any suggestions are welcomed.

 

[Alek Trishan]

Alek Trishan has written on 4/18/2014 12:56 PM:

I'm looking to replace my system drive (C) in a Windows 7 computer. It's
a 120GB SSD and I'm wondering whether I should just get another SSD or a
hybrid drive.

Any suggestions are welcomed.

It looks like net wisdom says that hybrids aren't worth it and that I
should get another SSD.

Are Crucial and Samsung the most reliable?

 

[Paul]

Alek Trishan has written on 4/18/2014 12:56 PM:

It looks like net wisdom says that hybrids aren't worth it and that I
should get another SSD.

Are Crucial and Samsung the most reliable?

I would buy one with MLC flash, rather than TLC.
But the TLC one could be cheaper.

SLC - stores one bit per cell, using two voltage levels (Enterprise class)
MLC - stores two bits per cell, using four voltage levels (Consumer class)
TLC - stores three bits per cell, using eight voltage levels (Consumer class)

MLC and TLC are somewhere in the 3000 write cycle range, for write
endurance. TLC is probably using a stronger ECC code in the design
of the flash chips, which means a couple percent of the extra capacity
gets used up providing additional strength for error correcting on read.
All flash uses error correction, even SLC. The more dense the storage,
the more additional bytes per sector needed to provide decent error correction.

When buying a drive, you look at the progression of transfer
speed versus capacity.

Lowest capacity - kinda slow
Lower middle capacity - a bit faster
Upper middle capacity - full speed <--- sweet spot, all channels occupied
Top capacity - full speed

You only buy enough capacity, to get full operating speed. That
gives you the best performance for the purchase.

The worst case operation the computer does to the flash, is 4K random
read/write. Such a pattern might happen with a pagefile. Or perhaps
during defragmentation (but normally the OS doesn't defragment
an SSD, defragment is turned off). Intel drives were the first ones
to take that seriously. You would look for various benchmark
pages, to see if your planned purchase does well on that test.
The test isn't particularly good for the drive, but if the
OS does that to a drive, you want the drive to perform
well while enduring it.

*******

Sorting the SSD drives on Newegg by customer review rating,
and looking at specs and price, Samsung has a pretty strong
showing there. The Crucial showing in the list, weren't
even close.

This Crucial is pretty cheap ($80), but the sequential write
is about the same as a hard drive. The seek speed will be much
better than a hard drive. So it is still better than a hard
drive.

http://www.newegg.com/Product/Product.aspx?Item=N82E16820148693

I have to go to a $240 drive (3x price for 4x capacity), to
get the full speed (all channels full). Flash type is MLC
and controller is Marvell. When I go through the customer
reviews, I can see a few reports of lemons.

http://www.newegg.com/Product/Product.aspx?Item=N82E16820148695

Just take your time and go through the reviews. You'll soon
see who delivers on "lemons" or not. And if you can, try
to select a product with MLC. At one time, I would have said
select one with SLC, but I haven't seen one of those in the
listing for a while. The price for one of those would likely
be too high anyway.

The "lemon like" behavior comes from bad firmware, as much
as bad flash. The flash shouldn't be wearing out when the
drive is new, so that means for the ones I was looking at
there, it's likely to be a firmware issue. The history of SSD,
is full of bad firmware. Which leads to "instant" loss of data
cases, and my recommendation to bump up the backup frequency
(to an external hard drive).

Paul

 

[philo]

Alek Trishan has written on 4/18/2014 12:56 PM:

It looks like net wisdom says that hybrids aren't worth it and that I
should get another SSD.

Are Crucial and Samsung the most reliable?

I have a hybrid in my machine and it does not seem to perform any better
than any standard type SATA drive.

For best performance you might as well get another SSD

 

[Paul]

I have a hybrid in my machine and it does not seem to perform any better
than any standard type SATA drive.

For best performance you might as well get another SSD

They mention a "host-optimized mode" here, which uses
code in the OS to recognize what things to cache in
the Flash section. Without that, I would expect the drive
would be pretty useless at identifying what to cache.

http://en.wikipedia.org/wiki/Hybrid_drive

"In this mode of operation, the SSHD enables an extended
set of SATA commands defined in the Hybrid Information
feature of the Serial ATA International Organization
standards for the SATA interface. Using this feature,
decisions about which data elements are placed in the
NAND flash memory come from the host operating system"

"Specific features of SSHD drives such as host-hinted
LBA caching (see host-optimized mode above) require
operating system support. Microsoft added support
for these features into Windows 8.1."

I'd never heard of that before, and just found it in
that article. I thought all these things were dumb.
Without that, all a drive could do, is perhaps watch
clusters that get more accesses than others (having
the host help you, should help a lot).

Another thing I'm curious about, is whether the hybrid
drive is able to just ignore the flash section, when
a flash chip fails. And run as a regular drive, without
taking all the user data with it (as an outright device failure).

Paul

 

[~misfit~]

They mention a "host-optimized mode" here, which uses
code in the OS to recognize what things to cache in
the Flash section. Without that, I would expect the drive
would be pretty useless at identifying what to cache.

http://en.wikipedia.org/wiki/Hybrid_drive

"In this mode of operation, the SSHD enables an extended
set of SATA commands defined in the Hybrid Information
feature of the Serial ATA International Organization
standards for the SATA interface. Using this feature,
decisions about which data elements are placed in the
NAND flash memory come from the host operating system"

"Specific features of SSHD drives such as host-hinted
LBA caching (see host-optimized mode above) require
operating system support. Microsoft added support
for these features into Windows 8.1."

I'd never heard of that before, and just found it in
that article. I thought all these things were dumb.
Without that, all a drive could do, is perhaps watch
clusters that get more accesses than others (having
the host help you, should help a lot).

Another thing I'm curious about, is whether the hybrid
drive is able to just ignore the flash section, when
a flash chip fails. And run as a regular drive, without
taking all the user data with it (as an outright device failure).

Hi Paul. That was an interesting read, thanks. I am very financially
constrained but love my (pimped) T60 ThinkPad (still running XP but likely
to go to W7 soon) and was watching Seagate's development of the Momentus XT
and it seems I jumped at just the right time.

The first model used 4GB of Intel SLC NAND with 500GB of 7,200rpm platters
and apparently they had a few issues with their algorithms - it wasn't as
good as it could have been. The second model had 8GB Intel SLC and 750GB
7,200rpm platters and Seagate said they'd got the caching sorted - so I
bought one and it's been great!

I'm really pleased I didn't wait for the third iteration as that uses 8GB of
*MLC* and the platters (500 or 1,000GB) only spin at 5,400rpm. I too wonder
what happens if / when the NAND dies so am chuffed that I didn't wait longer
and get an MLC model. As soon as they were announced the SLC versions
vanished from the market, I figure they were snapped up, there wasn't the
usual overlap where some vendors would still have old stock.

I've been eyeing up WDs Black2 but it's still much too expensive for me and
likely not a good idea while I'm using XP.

http://www.anandtech.com/show/7682/the-wd-black2-review

Cheers,
--
</Shaun>

"Humans will have advanced a long, long, way when religious belief has a
cozy little classification in the DSM."
David Melville (in r.a.s.f1).