12 Oct
2011
12 Oct
'11
6:52 p.m.
[[ Just realised when I sent this yesterday it went only to Andy and not
the list - Phil]]
On 10/10/2011 16:43, Andy Smith wrote:
Hi Phil,
On Fri, Oct 07, 2011 at 08:29:23AM +0100, Phil Stewart wrote:
OCZ use Sandforce controllers for their Vertex range; for Sandforce
controllers it's the SF-1500 (old) and SF-2500 (new) series controllers
which support power loss circuits - see this graphic from Anandtech:
http://images.anandtech.com/reviews/storage/OCZ/Vertex3/sflineup.jpg
Pretty much all OCZ's Vertex and Agility range use the SF-1222 (Vertex
2) and SF-2282 (Vertex 3), so don't feature power fail protection
circuits. OCZ did preview the Vertex 3 Pro using the SF-2582, but I'm
not sure this drive ever went on sale (you may still be able to get
Vertex 2 Pros with the SF-1522 though)
On 06/10/2011 20:32, Andy Smith wrote:
Do they
typically mention this in the specs? I am concerned because
the afewmoreamps.com link I posted above was using the relatively
new OCZ Vertex 3 and were still seeing this issue.
If they say "Enhanced power-loss data protection" in the specs, is
this what we're talking about? That's on Intel spec sheets; I don't
know what the equivalent might be for e.g. OCZ.
Given that they can lose transactions on Vertex 3 I think that we
can assume that no Vertex 2 or 3 SSD has this power loss
protection. SSDs can lose transactions if they are abruptly
powered off, even if
you disable their write cache:
http://www.evanjones.ca/intel-ssd-durability.html
http://www.afewmoreamps.com/2011/08/fsync-durability.html
One of the
differences (particularly on newer models) between consumer
and enterprise SSDs is enterprise models tend to come with a big power
cap to ensure pending writes can be completed in the event of power loss. 
How do you work out which products are
"enterprise"?
http://www.span.com/index.php?cPath=73_499_1452&page=1&sort=221d
The above URL shows some Intel X25-Ms as being more expensive than
Intel 320s of the same capacity.
This discrepancy is probably due to a move to 25nm NAND on the 320: die
shrinks result in doubling of capacity per chip, so you need half as
many chips to hit a capacity point. 25nm NAND also tends to be rated for
fewer write cycles.
Of these, Span thinks only the Intel 510 is
"enterprise". It doesn't list "Enhanced power-loss data
protection"
on its actual spec sheet though, whereas the Intel 320 does.
It looks like the major differences between the 320 and the 510 are that
the 510 is a SATA 3 (6Gbps) drive using the Marvell controller coupled
with 34nm (more chips so more performance, more write cycles). At a
glance, it looks more like an 'enthusiast' type drive geared towards
performance at the expense of dropping features like power protection
and encryption (take a look at
http://www.anandtech.com/show/4421/the-2011-midrange-ssd-roundup for
more details). I would also expect it to get replaced with a varient
using 25nm flash at some point as production of 34nm winds down.
The cheapest Intel 710 that Span do seems to be
£4.72/GB:
http://www.span.com/product_info.php?products_id=35173
That is about 3 times what I was hoping to spend, indeed. Just
buying more servers/spindles probably becomes cheaper, at that
point.
Yeah, it does look like the 710 is crazy expensive. To me, it looks like
the 320 at either 160Gb or 300Gb capacities is the way to go. I strongly
recommend taking a look at the SSD reviews on Anandtech though, as
they're extremely well versed on the fine detail and have good
benchmarking methodology (albeit geared more towards desktop/workstation
usage patterns, although I think they are doing more reviews of
enterprise SSD stuff now - it's been about 6 months since I got my SSD
so I'm not totally up-to-date anymore). For convenience, the 320 review
can be found on http://www.anandtech.com/show/4244/intel-ssd-320-review
, but it's certainly worth reading up on other stuff too if only for the
technical coverage you get.
--
Phil