
Exploring ZFS ZIL with Intel Optane and NAND - olavgg
https://www.servethehome.com/exploring-best-zfs-zil-slog-ssd-intel-optane-nand/
======
PascLeRasc
I'm a little surprised that they didn't standardize the SSD capacity, or
perform tests on empty vs nearly-full SSDs. Increasing size slightly decreases
read speeds, just like L3 caches.

~~~
benjaminl
The amount of space used by he ZIL on a SLOG is very modest. Typically less
than a gigabyte. So a SSD used as a SLOG will be practically empty it's entire
life. The reason one would use a large capacity SSD for this purpose is to
take advantage of the large SSD's higher iops and greater wear leveling.

~~~
BrainInAJar
it's unfortunate but not surprising that you can't buy very small, very fast
SSD's for this purpose

~~~
wmf
PMC-Sierra/Microsemi has some cool DRAM-based SSDs that do 1M IOPS (not a
typo) with 16GB capacity. [https://www.microsemi.com/product-
directory/storage-boards/3...](https://www.microsemi.com/product-
directory/storage-boards/3690-flashtec-nvram-drives) I don't think they're
available in U.2 or M.2 format though.

NVDIMM-N would probably also be great for slog.
[https://www.anandtech.com/show/12029/micron-
announces-32gb-d...](https://www.anandtech.com/show/12029/micron-
announces-32gb-ddr4-nvdimmn-modules)

~~~
wtallis
Yeah, DRAM chips are the only ones that currently offer the right balance of
performance and capacity per die. NAND and 3D XPoint dies are too big and too
slow per die for this use case, so they're better used as nonvolatile storage
to flush the log to in the event of power failure, not as the primary log
storage media.

I expect it will soon become common for high-end enterprise NVMe SSDs to
include a few GB of DRAM accessible through the new Persistent Memory Region
feature, so that they can be accessed through simple PCIe memory read and
write operations, but will automatically be preserved by the SSD in the event
of a power failure. It won't be as fast as a NVDIMM, but works with existing
form factors and platforms.

~~~
StudentStuff
Battery backed DRAM is likely a better choice for performance & endurance in
most applications, as the Optane product line is a lame duck with memory that
dies around the 1TB of writes mark, leaving you with lost data and a dead SSD.

~~~
wtallis
> as the Optane product line is a lame duck with memory that dies around the
> 1TB of writes mark, leaving you with lost data and a dead SSD.

You seem to be much more concerned with venting anger than conveying accurate
or relevant information.

~~~
Dylan16807
Considering that the Intel drive in [https://techreport.com/review/26523/the-
ssd-endurance-experi...](https://techreport.com/review/26523/the-ssd-
endurance-experiment-casualties-on-the-way-to-a-petabyte) self-destructed when
it ran out of guaranteed lifetime, I think it's a fair criticism.

~~~
wtallis
There's nothing fair about making up a number that's wrong by multiple orders
of magnitude.

I'm not a fan of the end of life behavior of Intel SSDs either, but it's a
consistent policy that does work well for enterprise usage scenarios, with no
unexpected data loss. They probably shouldn't be applying the same policy to
the consumer products. But the fact that there are valid criticisms to be made
doesn't mean this particular one was fair or germane.

~~~
Dylan16807
Oh, I wasn't even looking at the value of the number. Yeah, it's bad to
exaggerate like that without being clear about it. But something performance-
heavy can burn out an endurance of 10 drive writes per day _pretty fast_.

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unethical_ban
I am certain the volume of acronyms is intentionally hilarious in the title,
so let me pre-empt the complaining by laughing at it. Definitions are in the
article.

~~~
earenndil
ZFS = Z File System, a next-generation file system from oracle ZIL = ZFS
Intent Log SSD = Solid State Drive, a type of long-term data storage system
with better read/write speeds than an HDD NAND = not actually an acronym, but
a type of logic gate. Not AND.

~~~
empthought
Hilariously enough, NAND is the only acronym. The others are initialisms.

~~~
ajnin
Initialisms _are_ acronyms.

~~~
wnoise
Other way around. Acronyms are the subset of initialisms that are
pronounceable.

~~~
cmurf
Dictionary.com uses same definitions for both words, just in a different
order. The first definition of acronym is when initials form a pronounced
word; which is the second definition of initialism. So they're the same thing
with the difference being vernacular.

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brian-armstrong
So we know the CPUs have IME. What else? Is it conceivable that SSDs do as
well? Is any Intel product safe to use?

~~~
wmf
No, nothing is safe. There's an NSA backdoor in your mouse.

~~~
r00fus
you jest, certainly, yet... now I'm not sure.

~~~
arca_vorago
They are called implants.[1] To GP, yes even hdds, I suspect similar with
ssds.[2]

1:
[https://www.schneier.com/blog/archives/2014/03/cottonmouth-i...](https://www.schneier.com/blog/archives/2014/03/cottonmouth-
i_n.html)

2:
[http://spritesmods.com/?art=hddhack&page=1](http://spritesmods.com/?art=hddhack&page=1)

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tw04
This article reeks of being "sponsored" by Intel, but there is no mention of
it anywhere in the article. So my first question is - what, if any role did
Intel play in the creation of this article?

Second - I find it ironic after all the marketing buzz that Intel has finally
admitted that the endurance of Optane is embarrassing compared to NAND
devices. This was their original claim:

>When Intel announced 3D XPoint, the company said that it would be 1,000 times
faster than NAND flash, 10 times denser than (volatile) DRAM, and with 1,000
times the endurance of NAND

Those claims are so far off from reality that I'm surprised their shareholders
haven't sued them over the claims.

~~~
wmf
ServeTheHome is one of the most honest hardware review sites, especially in
the very small field of server/enterprise hardware. AFAIK ServeTheHome is
basically advertising for DemoEval which is an independent lab full of servers
that you can rent access to. So there's a commercial interest behind it, but
it's not Intel.

Here's their policy if you want to believe it:
[https://www.servethehome.com/about/editorial-copyright-
polic...](https://www.servethehome.com/about/editorial-copyright-policies/)

Looking at Optane specifically, it is just that good. It is 2x-10x better than
NAND (at ~2x the price) in certain aspects like mixed read/write or fsync.
This is very far from Intel's 1000x claims, but Optane is still worth buying
in some cases.

(Also, feel free to call me a paid shill if you want to get deeper in the
mud.)

~~~
tw04
2x-10x better when they claimed 1000x isn't "just that good". ESPECIALLY not
when the write endurance is so abysmal.

The fact they don't come out and say, in the review, the hardware was
furnished by Intel, and instead you have to actively search out the link you
just provided, in and of itself is troubling. It's common courtesy and pretty
much industry standard practice to list conflicts of interest at the start or
end of an article like the one posted...

~~~
Patrick-STH
Hi tw04 - just as a heads up, none of the SSDs were furnished by Intel. We
have a budget and bought all of the drives we used on this test. Some we had
to buy second hand, some were scavenged from servers we have had to
decommission.

Intel does provide us with hardware, as does AMD, Intel, Toshiba, Samsung,
WDC, Cavium and etc. In fact, we have a full list of all relationships here:
[https://www.servethehome.com/about/editorial-copyright-
polic...](https://www.servethehome.com/about/editorial-copyright-policies/)

Unlike virtually every other major review site (and a large number of
bloggers), as of today we still do not have direct ad sales to any of these
companies.

We also buy an absolute ton of gear for the DemoEval service we run which is
why we have access to many different bits. For example, we have purchased a
dozen Optane 900p's already since Intel would not furnish us with a U.2 drive.

Intel does not want to have the 900p eat into the P4800X which is a higher
margin product. As a result, this is the kind of article (Optane 900p in
servers) that Intel specifically would not want us to do. Since we buy
hardware, we can.

~~~
wtallis
> Intel does not want to have the 900p eat into the P4800X which is a higher
> margin product. As a result, this is the kind of article (Optane 900p in
> servers) that Intel specifically would not want us to do. Since we buy
> hardware, we can.

Intel has not to my knowledge actively discouraged or tried to prevent anyone
from reviewing the 900p in an enterprise context. They haven't expressed any
negative opinion about me including the 900p in my review of the P4800X, even
though they provided hardware for both.

I agree that they probably don't want the 900p to hurt the sales of the
P4800X, but I don't think they're particularly concerned about that happening.
Most potential P4800X customers aren't going to go to the trouble of buying
and installing large quantities of 900ps instead.

