1TB Flash in 3.5" size?

lid wrote:
Arno kenjka:
Why are you referring to SSD drive and sequential writes? The main reason
why SSD are used are their high IOPS values! OK, I am talking from the
storage vendor perspective, and not from the home-user perspective...

I am talking sustained maximum write speed. Does not need to be
sequential, but it is the worst-case for the lifetime. Of course a lower
rate with small writes that still result in an effective write rate
(because of larger internal block size) of 200MB/s also hits this worst
case.

But SSD's in any serious enviroments are never used for sequential writes...
OLTP and similar enviroments need high IOPS, not MB/s... If you want MB/s,
go with a big bunch of SATA drives, and you'll get very cheap MB/s
performance...

You may have a combination of mostly sequential writes and under
some circumstances a lot of random reads. And yes, this can happen
in a serious environment as well although it requires a bit more
of a specual scenario.

So while your 150 years figure is certainly good to boost sales, it is
unusable to evaluate practical endurance. For that you need to look at the
particular worst case.

200MB/s is sequential read performance, and who knows what block size were
used... I stay with the 150 years, cause it's my calculation for STEC
ZeusIOPS drive used in EMC storage systems... So, here's the calculation:

400 * 10^9 * 100000 / 4000 / 2000 / 365 / 24 / 3600

400GB drive (400 * 10^9 Bytes)
SLC technology (100.000 E/W cycles)
4000 (block size is 4kBytes)
2000 (average write IOPS)
365 (days per year)
24 (hours per day)
3600 (seconds per hour)

The result is 158 years...

Ah, you assume writes fall into one block of 4kB and the disk
block size is 4kB. Then you have a write speed of 8MB/s and yes,
your number fits. I expect these are a bit more expensive ;-)

However mass-market SSDs have 128kB blocks or even larger
(not exposed to the OS). There you get much lower numbers.
An affordable SSD with 4kB block size would be nice in fact,
due to much better small write performance.

And there is a second problem. On power-fail a SSD can corrupt areas not
written to because of large internal block sizes. That means in
high-reliability applications you actually can only write it in a
sequential fashion and without filesystem as everything else is dangerous
to your data.

Nope... At least not with drives I was working with... They all have 64MB
cache that has battery backup... This can be a problem for SMB drives, but
not for enterprise...

Well, if you have RAM fronted SSD, you are in a different class anyways.
I remember that some Linux Filesystem people are starting to worry
about this, because it can kill journalling. There are some ways
around the problem, but only if the SSD exposes the block size.
Or if you have enough money for the expensive stuff ;-)

Sorry, but I am all into enterprise, and have totally lost touch with
reality in the normal SMB market...

No problem. When you can really throw money at the problem, the
solutions look a bit different. Mass market can give you similar
performance and reliability a lot cheaper, but you have to go
some extra steps and really need to know what you are doing.

Arno
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lid wrote:
Arno kenjka:
[...]
No problem. When you can really throw money at the problem, the solutions
look a bit different. Mass market can give you similar performance and
reliability a lot cheaper, but you have to go some extra steps and really
need to know what you are doing.

Well, my clients are buying, and are very affraid of SSD drives because of
the problems visible in mass market... So I need to explain them that these
SSD drives used in high-end equipment haven't got anything similar to mass
market SSD drives...

Ah, I see your problem. And it explains your stance, which I
think is justified on the equipment you are selling. If anybody
ever asks you about consumer-grade SSDs, give them my figures ;-)

Well, as I do understand the technology, I typically go for
mass-market, but my main application for large disk storage
so far was research data which was backed up on an enterprise
class tape library as well, so not really critical.

Arno
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Does anyone yet make a TB Flash memory in a 3.5" drive physical format. If
so, could you pass on a reference? The interface would need to support
about at a 400MB/s sustained rate. I can work with any interface such as
Fiber Channel or whatever .

$3,799 at newegg for SATA (claimed 260 MB/s read and write):
http://www.newegg.com/Product/Produc...82E16820227502

$3,799 at newegg for PCI express (claimed 600 MB/s write and
870 MB/s read ):
http://www.newegg.com/Product/Produc...82E16820227500

Lynn

"David Brown" wrote in message
...
Arno wrote:
trs80 wrote:
Does anyone yet make a TB Flash memory in a 3.5" drive physical format.
If so, could you pass on a reference? The interface would need to
support about at a 400MB/s sustained rate. I can work with any
interface such as Fiber Channel or whatever .
thanks for any tips

Nobody does and nobody gets that rate, not even for large accesses.
Although some manufacturers have SATA3 drives
planned with internal excessive multi channel architectures.
For small accesses FLASH can be significantly slower than
disks. For what you want, you may want to look at a traditional RAM
fronted disk. Will be expensive though and definitely
not available in 3.5". Alternatively you could build a RAID0 with a
really fast controller and FLASH disks. Arno


There are a number of very fast drives available, but the cost is
significant - a raid would be much more cost-effective. The biggest
single drive I found in a quick check was:

http://www.plianttechnology.com/lightning_ls.php

That's 300 GB in 3.5" SAS, rated at 525/340 MB/s.

Of course, for the fastest devices you use a PCI Express card with RAM
rather than flash...

The fastest and largest I have seen is the 1TB OCZ PCIe
SSD with read and write rates of 870MB/s and 780MB/s.
The part number is OCZSSDPCIE-ZDM841T, and the
price is a mere $4k approx.