Alek said:
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
