| Author |
Message |
flux
Guest
|
 Posted:
Wed Dec 01, 2004 11:34 am Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
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|
In article <41ac2963$1@news.infonet.ee>,
Toomas Soome <Toomas.Soome@microlink.ee> wrote:
| Quote: | current data transfer rates (lets not argue about possible future
numbers, I have some but never done research for them):
SATA: 150Mb/s (up to 1.5Gb/s?)
SCSI: 320Mb/s
SAS: 3Gb/s (roadmap up to 12Gb/s)?
FC-AL: 2Gb/s (roadmap up to 10Gb/s ?)
|
These numbers may also be irrelevant depending on how the data is being
accessed. If, for example, you are connected to a server over Ethernet,
even SATA is faster (taking the numbers at face value) than gigabit.
| Quote: | reliability:
SCSI MTBF 1,200,000 hours, many SATA drives only run to 600,000 MTBF
(http://searchstorage.techtarget.com/infoCenter/tip/0,294276,sid5 gci1001942
tax294586,00.html)
|
What do those numbers actually mean? 1,200,000 hours is 136 years.
So this number taken at face value is pretty silly because it's
essentially saying it won't be until sometime in 22nd century before
just first SCSI hard disk anywhere on Earth fails!
Even not taken these numbers at face value, who is going to buy SATA
drives and keep them for several years? As long as they last through the
warranty period, you can just buy new ones. They are, after all, very
cheap. And you can bet the next generation will be bigger, better,
faster (e.g, SATA II), and cheaper. |
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flux
Guest
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| Posted:
Wed Dec 01, 2004 11:51 am Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
In article <313n27F383t0aU1@uni-berlin.de>,
"Nik Simpson" <n_simpson@bellsouth.net> wrote:
| Quote: | The SCSI interface per-se doesn't, but because SCSI & FC drives are designed
for "enterprise class" applications they go through a different & more
rigourous quality control process than consumer drives. It's this more
comprehensive QC that is responsible for better reliability rather than the
interface. So in the future there is no technical reason why the SATA drives
|
Is this really the case?
Checking on Maxtor's site,
http://www.maxtor.com/portal/site/Maxtor/menuitem.a14629af82eff9461400585
760b46068/?channelpath=/en_us/Support/Warranty%20Services/Warranty%20Peri
ods
It looks like the "plain" Maxtor's get a 3 year warranty and the
"high-end" get five, same as their SCSI counterparts.
It's not really obvious how this QC gets translated into a 2 year
difference.
Further, three years doesn't seem to be a really short life with respect
to computer hardware. Given how cheap SATA disks are, who would even
keep them around for that long, especially if you needed more space in
their place by that time? |
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flux
Guest
|
| Posted:
Wed Dec 01, 2004 12:15 pm Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
In article <ybt7jo35nye.fsf@isis.visi.com>, Anton Rang <rang@visi.com>
wrote:
| Quote: | SATA disks typically have less error checking internally than SCSI,
|
How do you know this?
| Quote: | increasing the likelihood of undetected errors. Not a big deal if
you're working with 1 disk; more serious when you have 10 and
|
I don't get it. How is not a big deal if you are working with one disk?
If a single bit gets flipped and it happens to be in your OS's kernel
file or your government grant application worth a million dollars, it
could be very serious. |
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Malcolm Weir
Guest
|
| Posted:
Wed Dec 01, 2004 1:49 pm Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
On Wed, 01 Dec 2004 06:34:59 GMT, flux <support@fluxsoft.com> wrote:
| Quote: | In article <41ac2963$1@news.infonet.ee>,
Toomas Soome <Toomas.Soome@microlink.ee> wrote:
current data transfer rates (lets not argue about possible future
numbers, I have some but never done research for them):
SATA: 150Mb/s (up to 1.5Gb/s?)
SCSI: 320Mb/s
SAS: 3Gb/s (roadmap up to 12Gb/s)?
FC-AL: 2Gb/s (roadmap up to 10Gb/s ?)
These numbers may also be irrelevant depending on how the data is being
accessed. If, for example, you are connected to a server over Ethernet,
even SATA is faster (taking the numbers at face value) than gigabit.
|
Only if the network traffic has a 1:1 correspondence with the disk
traffic. This is very, very rare in large environments. Plus you
have forgotten that Ethernet is full-duplex...
And I'd note that *two* 1000BaseT networks deliver more bandwidth than
one...
| Quote: | reliability:
SCSI MTBF 1,200,000 hours, many SATA drives only run to 600,000 MTBF
(http://searchstorage.techtarget.com/infoCenter/tip/0,294276,sid5 gci1001942
tax294586,00.html)
What do those numbers actually mean? 1,200,000 hours is 136 years.
|
It means that if you have 136 of them, one will fail every year during
their service life.
| Quote: | So this number taken at face value is pretty silly because it's
essentially saying it won't be until sometime in 22nd century before
just first SCSI hard disk anywhere on Earth fails!
|
Not at all. The figure was calculated with (I'd bet) no more than a 5
year service life. You can predict *nothing* about what happens after
the service lifespan is exceeded. In other words, every single drive
could fail a week after it's fifth birthday without impacting that
number at all!
| Quote: | Even not taken these numbers at face value, who is going to buy SATA
drives and keep them for several years? As long as they last through the
warranty period, you can just buy new ones. They are, after all, very
cheap. And you can bet the next generation will be bigger, better,
faster (e.g, SATA II), and cheaper.
|
The cost of managing large disk populations tends to make that idea a
very expensive one. Suppose you have 1,000 disks and a 3 year
expected life. That works out to replacing a disk every single
working day. Up the life to 5 years, and you get a day off every
week!
Malc. |
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J. Clarke
Guest
|
| Posted:
Wed Dec 01, 2004 9:11 pm Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
flux wrote:
| Quote: | In article <41ac2963$1@news.infonet.ee>,
Toomas Soome <Toomas.Soome@microlink.ee> wrote:
current data transfer rates (lets not argue about possible future
numbers, I have some but never done research for them):
SATA: 150Mb/s (up to 1.5Gb/s?)
SCSI: 320Mb/s
SAS: 3Gb/s (roadmap up to 12Gb/s)?
FC-AL: 2Gb/s (roadmap up to 10Gb/s ?)
These numbers may also be irrelevant depending on how the data is being
accessed. If, for example, you are connected to a server over Ethernet,
even SATA is faster (taking the numbers at face value) than gigabit.
reliability:
SCSI MTBF 1,200,000 hours, many SATA drives only run to 600,000 MTBF
(http://searchstorage.techtarget.com/infoCenter/tip/0,294276,sid5
gci1001942 tax294586,00.html)
What do those numbers actually mean? 1,200,000 hours is 136 years.
So this number taken at face value is pretty silly because it's
essentially saying it won't be until sometime in 22nd century before
just first SCSI hard disk anywhere on Earth fails!
|
That's not the service life--it doesn't take wear into consideration. If
you have say 140 drives then you should expect one failure every year out
of that 140.
| Quote: | Even not taken these numbers at face value, who is going to buy SATA
drives and keep them for several years? As long as they last through the
warranty period, you can just buy new ones. They are, after all, very
cheap. And you can bet the next generation will be bigger, better,
faster (e.g, SATA II), and cheaper.
|
For enterprise storage replacing drives every two years would be very
costly. The price of the drives is peanuts compared to the cost of
downtime.
--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net) |
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J. Clarke
Guest
|
| Posted:
Wed Dec 01, 2004 9:14 pm Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
flux wrote:
| Quote: | In article <313n27F383t0aU1@uni-berlin.de>,
"Nik Simpson" <n_simpson@bellsouth.net> wrote:
The SCSI interface per-se doesn't, but because SCSI & FC drives are
designed for "enterprise class" applications they go through a different
& more rigourous quality control process than consumer drives. It's this
more comprehensive QC that is responsible for better reliability rather
than the interface. So in the future there is no technical reason why the
SATA drives
Is this really the case?
Checking on Maxtor's site,
http://www.maxtor.com/portal/site/Maxtor/menuitem.a14629af82eff9461400585
760b46068/?channelpath=/en_us/Support/Warranty%20Services/Warranty%20Peri
ods
It looks like the "plain" Maxtor's get a 3 year warranty and the
"high-end" get five, same as their SCSI counterparts.
|
By that reasoning Hyundai makes the best car on Earth. Warranty length is
related to marketing concerns, not to durability.
| Quote: | It's not really obvious how this QC gets translated into a 2 year
difference.
|
It doesn't. Marketing decided that to sell drives in their target market
they needed a 5 year warranty, and they built the cost of that into the
price of the drive.
| Quote: | Further, three years doesn't seem to be a really short life with respect
to computer hardware. Given how cheap SATA disks are, who would even
keep them around for that long, especially if you needed more space in
their place by that time?
|
Any enterprise that was using them for mission-critical storage. Don't
assume that the enterprise market is like a home user who can shut his
machine down on a whim.
--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net) |
|
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J. Clarke
Guest
|
| Posted:
Wed Dec 01, 2004 9:15 pm Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
flux wrote:
| Quote: | In article <ybt7jo35nye.fsf@isis.visi.com>, Anton Rang <rang@visi.com
wrote:
SATA disks typically have less error checking internally than SCSI,
How do you know this?
increasing the likelihood of undetected errors. Not a big deal if
you're working with 1 disk; more serious when you have 10 and
I don't get it. How is not a big deal if you are working with one disk?
If a single bit gets flipped and it happens to be in your OS's kernel
file or your government grant application worth a million dollars, it
could be very serious.
|
The more disks you have the more likely you'll get an error.
--
--John
Reply to jclarke at ae tee tee global dot net
(was jclarke at eye bee em dot net) |
|
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Peter
Guest
|
| Posted:
Wed Dec 01, 2004 11:17 pm Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
| Quote: | reliability:
SCSI MTBF 1,200,000 hours, many SATA drives only run to 600,000 MTBF
(http://searchstorage.techtarget.com/infoCenter/tip/0,294276,sid5
gci1001942
tax294586,00.html)
What do those numbers actually mean? 1,200,000 hours is 136 years.
So this number taken at face value is pretty silly because it's
essentially saying it won't be until sometime in 22nd century before
just first SCSI hard disk anywhere on Earth fails!
|
You are completely wrong (did you ever studied statistics?).
Let me quote:
"MTBF is an abbreviation for Mean Time Between Failures.
MTBF is a measure of how reliable a product is. MTBF is usually given in
units of hours; the higher the MTBF, the more reliable the product is.
For electronic products, it is commonly assumed that during the useful
operating life period the parts have constant failure rates, and part
failure rates follow an exponential law of distribution. In this case, the
MTBF of the product can be calculated as:
MTBF = 1/(sum of all the part failure rates)
and the probability that the product will work for some time T without
failure is given by:
R(T) = exp(-T/MTBF)
Thus, for a product with an MTBF of 250,000 hours, and an operating time of
interest of 5 years (43,800 hours):
R = exp(-43800/250000) = 0.839289
which says that there is an 83.9% probability that the product will operate
for the 5 years without a failure, or that 83.9% of the units in the field
will still be working at the 5 year point."
It means that during 5 years, for a 1,000 disks in your enterprise,
36 disks will fail if MTBF is 1,200,000 hrs
or 70 disks will fail if MTBF is 600,000 hrs
or 136 disks will fail if MTBF is 300,000 hrs
Now, if every storage unit has RAID 1 (2 disks), and enterprise has 1,000
storage units,
1.3 storage units will fail if MTBF of each disk is 1,200,000 hrs
5 storage units will fail if MTBF of each disk is 600,000 hrs
18 storage units will fail if MTBF of each disk is 300,000 hrs
assuming that you are not paying attention (replacing) to dead disks. If you
replace dead drives at frequent intervals, reliabilty of RAID 1 storage
units will be even much higher. |
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Jesper Monsted
Guest
|
| Posted:
Thu Dec 02, 2004 5:07 am Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
"J. Clarke" <jclarke@nospam.invalid> wrote in
news:cokrhu0166f@news3.newsguy.com:
| Quote: | For enterprise storage replacing drives every two years would be very
costly. The price of the drives is peanuts compared to the cost of
downtime.
|
And any decent storage system should handle the replacement just fine,
using spare drives and/or rebuilding the ones replaced. You're not using a
big shiny box as a raid0 device, are you?
--
/Jesper Monsted |
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flux
Guest
|
| Posted:
Thu Dec 02, 2004 12:09 pm Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
In article <cokri01166e@news3.newsguy.com>,
"J. Clarke" <jclarke@nospam.invalid> wrote:
| Quote: | It looks like the "plain" Maxtor's get a 3 year warranty and the
"high-end" get five, same as their SCSI counterparts.
By that reasoning Hyundai makes the best car on Earth. Warranty length is
related to marketing concerns, not to durability.
|
No, your analogy doesn't fly because warranties cost money if the drives
have a high-failure rate. The reason companies can offer warranties of
such lengths is because their products are least durable enough to make
it cost-effective.
The fact that SATA and SCSI have similar warranties clearly indicates
the companies have enough confidence in SATA that they consider it
durable.
A logical rebuttal might be that manufacturers could offer lifetime
warranties on SCSI drives because they are just that durable, but a
warranty that long doesn't make sense from a marketing point of view
because the manufacturers do want their customers to upgrade eventually.
| Quote: | It's not really obvious how this QC gets translated into a 2 year
difference.
It doesn't. Marketing decided that to sell drives in their target market
they needed a 5 year warranty, and they built the cost of that into the
price of the drive.
|
It clearly does. If the failure rate for drives increases in the fourth
and fifth year, it will cost the company money to replace the broken
drives.
| Quote: | Further, three years doesn't seem to be a really short life with respect
to computer hardware. Given how cheap SATA disks are, who would even
keep them around for that long, especially if you needed more space in
their place by that time?
Any enterprise that was using them for mission-critical storage. Don't
assume that the enterprise market is like a home user who can shut his
machine down on a whim.
|
This is also illogical. It's like saying you can't ever upgrade. |
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flux
Guest
|
| Posted:
Thu Dec 02, 2004 12:12 pm Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
In article <316g5qF3896noU1@individual.net>,
"Peter" <peterfoxghost@yahoo.ca> wrote:
| Quote: | reliability:
SCSI MTBF 1,200,000 hours, many SATA drives only run to 600,000 MTBF
(http://searchstorage.techtarget.com/infoCenter/tip/0,294276,sid5
gci1001942
tax294586,00.html)
What do those numbers actually mean? 1,200,000 hours is 136 years.
So this number taken at face value is pretty silly because it's
essentially saying it won't be until sometime in 22nd century before
just first SCSI hard disk anywhere on Earth fails!
You are completely wrong (did you ever studied statistics?).
|
Reread what I wrote carefully, and you will see that is quite correct. |
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flux
Guest
|
| Posted:
Thu Dec 02, 2004 12:13 pm Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
In article <cokrhu0166f@news3.newsguy.com>,
"J. Clarke" <jclarke@nospam.invalid> wrote:
| Quote: | For enterprise storage replacing drives every two years would be very
costly. The price of the drives is peanuts compared to the cost of
downtime.
|
This seems to imply nobody ever buys new equipment. |
|
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flux
Guest
|
| Posted:
Thu Dec 02, 2004 12:21 pm Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
In article <gr0rq0153drf7fhg9didasoe8154nuerds@4ax.com>,
Malcolm Weir <malc@gelt.org> wrote:
| Quote: | Only if the network traffic has a 1:1 correspondence with the disk
traffic. This is very, very rare in large environments. Plus you
have forgotten that Ethernet is full-duplex...
|
I don't know whether to interpret this as saying everyone is on a very
slow network or a very fast network. Those scenarios are probably very
rare, so either way, it supports my argument. SATA is plenty fast enough
on a server to handle clients are an ordinary Ethernet network. |
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Malcolm Weir
Guest
|
| Posted:
Thu Dec 02, 2004 1:54 pm Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
On Thu, 02 Dec 2004 07:21:47 GMT, flux <support@fluxsoft.com> wrote:
| Quote: | In article <gr0rq0153drf7fhg9didasoe8154nuerds@4ax.com>,
Malcolm Weir <malc@gelt.org> wrote:
Only if the network traffic has a 1:1 correspondence with the disk
traffic. This is very, very rare in large environments. Plus you
have forgotten that Ethernet is full-duplex...
I don't know whether to interpret this as saying everyone is on a very
slow network or a very fast network. Those scenarios are probably very
rare, so either way, it supports my argument. SATA is plenty fast enough
on a server to handle clients are an ordinary Ethernet network.
|
*Sigh* You don't get out much, do you?
Outside the trivial case of file and print serving, people use
applications like, say, databases.
Which means that a few bytes sent across the network (say, "SELECT x.y
where x.id = z and y.thing = 123") result in many, many disk accesses,
totalling gigabytes of IO.
Now, has it dawned on you that even the most rudimentary of network
servers has multiple NICs? Why do you think that is? Are server
manufacturers silly?
I strongly suspect that all your experience has been with the trivial
case, where you have (at most) a few file-sharing clients on a
network. In these case, you are right. But there's no money in that
market, since any fool can build such a system.
Where *hard* problems are, at least for those of us in
comp.arch.storage, it is assumed that the network problem is already
solved. Need 10GB/sec of network bandwidth and don't have a 10G
Ethernet? Simply trunk 10 1000BaseT nets to your switch! Cisco (and
the like) can handle that part of the problem.
Secondly, "very rare" is relative. In terms of "raw number of
installations", you could be right. In terms of "Organizations with
an IT budget in excess of $100000 per year", you are wrong.
Guess who the vendors care about?
Malc. |
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Malcolm Weir
Guest
|
| Posted:
Thu Dec 02, 2004 1:56 pm Post subject:
Re: What am I doing wrong ??? Or is Adaptec 21610SA just a c |
|
|
On Thu, 02 Dec 2004 07:13:57 GMT, flux <support@fluxsoft.com> wrote:
| Quote: | In article <cokrhu0166f@news3.newsguy.com>,
"J. Clarke" <jclarke@nospam.invalid> wrote:
For enterprise storage replacing drives every two years would be very
costly. The price of the drives is peanuts compared to the cost of
downtime.
This seems to imply nobody ever buys new equipment.
|
No, it doesn't. It implies that enterprises would rather replace
drives every three years, not every two, and would rather replace them
every four years than every three, etc.
Are you being deliberately obtuse?
Malc. |
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