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

trs80 <(E-Mail Removed)> 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

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David Brown <(E-Mail Removed)> wrote:
> Barry OGrady wrote:
>> On Sat, 6 Feb 2010 22:13:20 -0800, "trs80" <(E-Mail Removed)> 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
>>
>> Its not available yet, and remember flash ram is slow and has limited
>> read write cycles.
>>

> Flash drives are not normally considered "slow" - read performance of
> 200+ MB/s, and writes of maybe 70 MB/s are possible with good drives.
> That's a lot faster for reading than even top-range hard disks, and
> similar for writing (the OP doesn't specify if they want reading or
> writing speeds).

Indeed. however a RAID0 with relatively cheap disks will give you
200+MB/s read and write speeds for large accesses. A 4-way
RAID0 (possible at least with Linux software RAID and likely with
the xBSDs as well) should reach 400MB/s large access speed.

For small accesses the story is different, onlt a RAM frontend will
reach this speed here, FLASH may be even slower than disk here,
especially on write.

> I agree about the sizes - you don't get flash drives as big as 1 TB at
> the moment (at least, not in standard 3.5" formats).


> As for write endurance, you are about a decade out of touch...

> <http://www.storagesearch.com/ssdmyths-endurance.html>

Well, not for USB flash. I did recently torture a 2GB Kingston
USB to death and it had consistent data errors (with no error
meassege to make matter worse!) after about 3500 full overwrites.

Say the OP wants to overwrite his disk at 400MB/s, then 3500
full operwrites are reached after about 100 days of operation.

I expect SATA FLASH is better, but not all may be. What however
does not happen with modern FLASH is that writing a few 1000
times to a single location kills the drive. Traditional FLASH
without wear leveling had that problem, with some dying
after 10000...100000 writes to the same sector.

Arno
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great inputs. thanks for the help
"trs80" <(E-Mail Removed)> wrote in message
news:4Ssbn.22419$(E-Mail Removed)...
> 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
>

David Brown <(E-Mail Removed)> wrote:
> Arno wrote:
[...]
> Small read accesses are extremely fast with flash disks - far faster
> than with hard disks, since small reads are dominated by the seek times.

True.

> For small writes, it is certainly true that these are slower to complete
> on a flash disk than on a hard disk, and less efficient than streamed
> writes. But outside of synthetic benchmarks, so what? Small writes are
> cached by the OS - as far as the application is concerned, they happen
> almost instantaneously. And as long as you don't have too many of them
> flushing to the disk at the same time, the writes are not going to cause
> other performance issues for the flash disk - if the disk needs to read
> from the same flash chip, the erase/write can be paused temporarily.
> You'll only see a real-world problem if you are dealing with an
> application that makes small writes and lots of fsyncs, combined with an
> older flash drive that is poor at hiding the garbage collection.

>>> I agree about the sizes - you don't get flash drives as big as 1 TB at
>>> the moment (at least, not in standard 3.5" formats).
>>
>>
>>> As for write endurance, you are about a decade out of touch...
>>
>>> <http://www.storagesearch.com/ssdmyths-endurance.html>
>>
>> Well, not for USB flash. I did recently torture a 2GB Kingston
>> USB to death and it had consistent data errors (with no error
>> meassege to make matter worse!) after about 3500 full overwrites.
>>

> USB flash devices are generally optimised for low costs rather than high
> quality or high endurance. They also often have very poor erase block
> management, since they have few chips and also must minimise the risk of
> data loss if the device is removed unexpectedly. This means a single
> block write to the device can cause many erase/writes to the flash.

>> Say the OP wants to overwrite his disk at 400MB/s, then 3500
>> full operwrites are reached after about 100 days of operation.
>>

> He doesn't say whether he wants to stream reads or writes, or how long
> he wants to sustain the transfers. My guess would be that he'd like to
> break off writing and do the occasional read - there are not many
> applications which produce new data at a rate of 34 TB per day, nothing
> of which needs to be kept for more than forty minutes!

I can think of an application or two that needs this. Quite
specialized though.

So here is a question to the OP: What is your access profile?

>> I expect SATA FLASH is better, but not all may be. What however
>> does not happen with modern FLASH is that writing a few 1000
>> times to a single location kills the drive. Traditional FLASH
>> without wear leveling had that problem, with some dying
>> after 10000...100000 writes to the same sector.
>>

> Modern SLC flash chips will have endurance in the range of at least a
> million erase/writes if you are nice to them (i.e., keep them at room
> temperature). MLC devices used in cheaper disks have significantly
> lower endurance.

> So for continuous writing using good SLC disks, he's got an average of
> something like 80 years before write endurance is a problem.

Yes, but even cheaper MLCs should be at 100'000 cycles today, that
is why I find the 3500 overwrites figure I found so disappointing,
and this thing uses an Intel flash memory chip, not some unpranded
or Tier-3 vendor product.

Expensive SLC is very hard to break and should indeed survive
decades at full write rate.

Arno
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Arno <(E-Mail Removed)> kenjka:
> Yes, but even cheaper MLCs should be at 100'000 cycles today, that

MLC's often have at max 10.000 E/W cycles... SLC's have around 100.000...
Reference is EMC's and STEC documentation for EFD drives (in fact it's STEC
ZeusIOPS)...

> Expensive SLC is very hard to break and should indeed survive
> decades at full write rate.

My calculations say that 400GB SLC drive can last 150 years with 24/7/365
writes on it (SLC, 100.000 E/W cycles)...

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http://calypso-innovations.blogspot.com/

(E-Mail Removed)lid wrote:
> Arno <(E-Mail Removed)> kenjka:
>> Yes, but even cheaper MLCs should be at 100'000 cycles today, that

> MLC's often have at max 10.000 E/W cycles... SLC's have around 100.000...
> Reference is EMC's and STEC documentation for EFD drives (in fact it's STEC
> ZeusIOPS)...

>> Expensive SLC is very hard to break and should indeed survive
>> decades at full write rate.

> My calculations say that 400GB SLC drive can last 150 years with 24/7/365
> writes on it (SLC, 100.000 E/W cycles)...


Ok, say 400GB at 200MB/s. That gives 1.8 overwrites/h, i.e. about
55'000h, i.e. about 6.25 years. Sorry your math is off. And
the 6.25 years are with perfect wear leveling. Assuming my
experience of death after 3'500 cycles with 10'000 cycle MLC,
the disk could die as early as within 2 years.

Even 1'000'000 cycle MLC only gives you 20-60 years.

Arno
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Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: (E-Mail Removed)
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Arno <(E-Mail Removed)> kenjka:
> > My calculations say that 400GB SLC drive can last 150 years with 24/7/365
> > writes on it (SLC, 100.000 E/W cycles)...

> Ok, say 400GB at 200MB/s. That gives 1.8 overwrites/h, i.e. about
> 55'000h, i.e. about 6.25 years. Sorry your math is off. And
> the 6.25 years are with perfect wear leveling. Assuming my
> experience of death after 3'500 cycles with 10'000 cycle MLC,
> the disk could die as early as within 2 years.

> Even 1'000'000 cycle MLC only gives you 20-60 years.


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...


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http://calypso-innovations.blogspot.com/

(E-Mail Removed)lid wrote:
> Arno <(E-Mail Removed)> kenjka:
>> > My calculations say that 400GB SLC drive can last 150 years with 24/7/365
>> > writes on it (SLC, 100.000 E/W cycles)...

>> Ok, say 400GB at 200MB/s. That gives 1.8 overwrites/h, i.e. about
>> 55'000h, i.e. about 6.25 years. Sorry your math is off. And
>> the 6.25 years are with perfect wear leveling. Assuming my
>> experience of death after 3'500 cycles with 10'000 cycle MLC,
>> the disk could die as early as within 2 years.

>> Even 1'000'000 cycle MLC only gives you 20-60 years.


> 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.

And while the high IOP is one desirable parameter, it is not
the only one. For example an SSD can well be used for an external
filesystem journal. This is a mostly write and mostly sequential
write operation. However when you recover the journal the IOPs
are the bottleneck. So you may want to put your journal on the
SSD to bring recovery speed down dramatically. Or rollback
speed if it is a database journal.

For a home-user, OTOH, you may actually hit your figure. But
home users do not have 24/7 anyways.

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.

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.

The short summary is that SSDs have write issues that
you need to understand in order to decide whether to
use them or not. They shine on read IOPs though.

Arno
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Arno <(E-Mail Removed)> 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...

> 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...

> 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...

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

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