| Author |
Message |
Keve Nagy
Guest
|
 Posted:
Wed Sep 22, 2004 1:01 pm Post subject:
SATA drive on SCSI bus |
|
|
Good Morning Newsgroup,
I was wondering, what makes SCSI better than IDE/ATA/ATAPI/SATA.
More precisely what I really wonder about is if the SCSI controller and
the bus alone (not including the devices) can make the difference in
range of raliability, speed and services.
In details:
I came accross a small PCB that turns any SATA drive into a SCSI drive.
http://www.addonics.com/products/io/adsalvd160.asp
As SATA drives are way cheaper than SCSI drives (compare a 160 or 200 GB
drive for example), this might be an interesting gadget.
So this brought up the question, what makes a real SCSI drive to be a
real SCSI drive?
I am not a SCSI expert, I am only a SCSI user. I had experience with
different kinds of buses and I recognized that SCSI was the best for my
needs. Since then I mainly use SCSI. This explains why I have these
stupid questions. :-)
So, I wonder what relevant differences can be between a real (factory)
SCSI drive and a SATA drive connected to the SCSI bus using one of these
converters.
I assume (only assume) that having a SATA disk and one of these
converters connected to my U160 SCSI bus and an Adaptec 29160 controller
I can perform the same utilities I could on a factory SCSI disk, as
these are provided by the SCSI BIOS. This means low level formatting,
verifying, excluding tracks/sectors/cilinders, etc.
AFAIK a SATA drive is capable of up to 150 Mb/s speed while an U160 SCSI
is 160 Mb/s, so there should not be any significant performance
differences (again, in theory) comparing disks with similar geometry,
capacity and RPM.
So, is there something I am missing here, is there something I should
take into account?
The final task is to decide if it is worth to buy a SATA drive plus one
of these converters for about USD 110 instead of a more expensive
factory SCSI disk.
If you can help me in this decision or have any suggestion on this
topic, your comments and ideas are most welcome here.
Thanks,
Keve
--
If you need to reply directly:
keve(at)mail(dot)poliod(dot)hu |
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Goran Larsson
Guest
|
| Posted:
Wed Sep 22, 2004 2:29 pm Post subject:
Re: SATA drive on SCSI bus |
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|
In article <2rctbdF18cgqvU1@uni-berlin.de>,
Keve Nagy <no_spam@poliod.hu> wrote:
| Quote: | As SATA drives are way cheaper than SCSI drives
|
Some SATA drives are cheaper.
If you look at slow high capacity 7200 rpm SATA drives then they are
cheap, just like cheap slow ATA disks. If you look att fast 10000 rpm
SATA disks you will find that they are just as expensive as SCSI disks.
Looking at one Swedish online dealer I find that a 73GB 10000 rpm SATA
disk, a 250GB 7200 rpm SATA disk and a 73GB 10000 rpm SCSI disk are at
the same price point.
If you need the storage space and don't care so much for performance then
a big SATA disk and a SCSI adapter may make sense.
If you need performance then the fast SATA disk plus adapter will be
more expensive than the fast SCSI disk.
--
Göran Larsson http://www.mitt-eget.com/ |
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Ryo Kato
Guest
|
| Posted:
Wed Sep 22, 2004 3:55 pm Post subject:
Re: SATA drive on SCSI bus |
|
|
Keve Nagy <no_spam@poliod.hu> wrote:
| Quote: | I was wondering, what makes SCSI better than IDE/ATA/ATAPI/SATA.
|
Read any "scsi vs. ide"-related websites/documents/discussions of last 10
years.
| Quote: | More precisely what I really wonder about is if the SCSI controller
and the bus alone (not including the devices) can make the difference
in range of raliability, speed and services.
In details:
I came accross a small PCB that turns any SATA drive into a SCSI
drive. http://www.addonics.com/products/io/adsalvd160.asp
|
An ATA->SCSI adapter won't help you much. First it won't be such
compatible f.e. with RAID-controllers, and second the adapter can't
replace missing SCSI-functions on the drive.
You will just have a SATA-drive and you will feel only this SATA-drive,
it doesn't care if you use SATA- or SCSI-bus. Use a SATA-devices on a
SATA-controller and SCSI-devices on SCSI-controller, mixing them will
only end up in unnecessary costs.
- Ryo |
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Keve Nagy
Guest
|
| Posted:
Wed Sep 22, 2004 4:31 pm Post subject:
Re: SATA drive on SCSI bus |
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|
Ryo Kato wrote:
| Quote: | An ATA->SCSI adapter won't help you much. First it won't be such
compatible f.e. with RAID-controllers, and second the adapter can't
replace missing SCSI-functions on the drive.
Can you mention an example for these SCSI-functions, as this is exactly |
what I am trying to find out!
| Quote: | You will just have a SATA-drive and you will feel only this SATA-drive,
it doesn't care if you use SATA- or SCSI-bus. Use a SATA-devices on a
SATA-controller and SCSI-devices on SCSI-controller, mixing them will
only end up in unnecessary costs.
This sort of confirms my feelings towards this. |
But I'll wait a bit more to see if there are other opinions!
Keve
--
If you need to reply directly:
keve(at)mail(dot)poliod(dot)hu |
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Keve Nagy
Guest
|
| Posted:
Wed Sep 22, 2004 4:32 pm Post subject:
Re: SATA drive on SCSI bus |
|
|
Goran Larsson wrote:
| Quote: | Some SATA drives are cheaper.
If you look at slow high capacity 7200 rpm SATA drives then they are
cheap, just like cheap slow ATA disks. If you look att fast 10000 rpm
SATA disks you will find that they are just as expensive as SCSI disks.
Looking at one Swedish online dealer I find that a 73GB 10000 rpm SATA
disk, a 250GB 7200 rpm SATA disk and a 73GB 10000 rpm SCSI disk are at
the same price point.
This is interesting and I have not noticed it before. |
It does change the whole general idea.
Thanks for pointing it out!
Keve
--
If you need to reply directly:
keve(at)mail(dot)poliod(dot)hu |
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Ron Reaugh
Guest
|
| Posted:
Thu Sep 23, 2004 1:06 am Post subject:
Re: SATA drive on SCSI bus |
|
|
"Keve Nagy" <no_spam@poliod.hu> wrote in message
news:2rctbdF18cgqvU1@uni-berlin.de...
| Quote: | Good Morning Newsgroup,
I was wondering, what makes SCSI better than IDE/ATA/ATAPI/SATA.
|
It's not better but just different.
| Quote: | More precisely what I really wonder about is if the SCSI controller and
the bus alone (not including the devices) can make the difference in
range of raliability, speed and services.
In details:
I came accross a small PCB that turns any SATA drive into a SCSI drive.
http://www.addonics.com/products/io/adsalvd160.asp
As SATA drives are way cheaper than SCSI drives (compare a 160 or 200 GB
drive for example), this might be an interesting gadget.
So this brought up the question, what makes a real SCSI drive to be a
real SCSI drive?
|
Onboard command queuing optimizations which SATA drives will have shortly.
Such is only relevant to saturated small record random I/O
performance(database servers).
SCSI has the disadvantage of higher command overhead so an SATA drive using
such a gadget on a SCSI bus will have DIMINISHED performance compared to
using a native SATA PCI card.
You will find that there are server offerings using SATA drives and
generally SCSI is NOT involved.
| Quote: | I am not a SCSI expert, I am only a SCSI user. I had experience with
different kinds of buses and I recognized that SCSI was the best for my
needs. Since then I mainly use SCSI. This explains why I have these
stupid questions. :-)
So, I wonder what relevant differences can be between a real (factory)
SCSI drive and a SATA drive connected to the SCSI bus using one of these
converters.
I assume (only assume) that having a SATA disk and one of these
converters connected to my U160 SCSI bus and an Adaptec 29160 controller
I can perform the same utilities I could on a factory SCSI disk, as
these are provided by the SCSI BIOS.
|
Some.
| Quote: | This means low level formatting,
|
Not possible on an SATA drive.
| Quote: | verifying, excluding tracks/sectors/cilinders, etc.
|
Nope.
| Quote: | AFAIK a SATA drive is capable of up to 150 Mb/s speed while an U160 SCSI
is 160 Mb/s,
|
That's the speed of the interface and not the drive inself. The fastest
SCSI drive can do about 79MB/sec. and the fastest [S]ATA drive about
70MB/sec.
| Quote: | so there should not be any significant performance
differences (again, in theory) comparing disks with similar geometry,
capacity and RPM.
So, is there something I am missing here, is there something I should
take into account?
|
Don't put SATA drives on a SCSI bus.
| Quote: | The final task is to decide if it is worth to buy a SATA drive plus one
of these converters for about USD 110 instead of a more expensive
factory SCSI disk.
|
Dump SCSI and use [S]ATA on a single user workstation. SCSI buys one
nothing on single user workstations. |
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Ron Reaugh
Guest
|
| Posted:
Thu Sep 23, 2004 1:10 am Post subject:
Re: SATA drive on SCSI bus |
|
|
"Goran Larsson" <hoh@invalid.invalid> wrote in message
news:I4FuGE.ILC@approve.se...
| Quote: | In article <2rctbdF18cgqvU1@uni-berlin.de>,
Keve Nagy <no_spam@poliod.hu> wrote:
As SATA drives are way cheaper than SCSI drives
Some SATA drives are cheaper.
If you look at slow high capacity 7200 rpm SATA drives then they are
cheap, just like cheap slow ATA disks. If you look att fast 10000 rpm
SATA disks you will find that they are just as expensive as SCSI disks.
|
NO!
| Quote: | Looking at one Swedish online dealer I find that a 73GB 10000 rpm SATA
disk, a 250GB 7200 rpm SATA disk and a 73GB 10000 rpm SCSI disk are at
the same price point.
|
You'll find that the SCSI was an older slower model and can't keep up with a
WDC Raptor on a single user workstation.
| Quote: | If you need the storage space and don't care so much for performance then
a big SATA disk and a SCSI adapter may make sense.
|
NO, the big SATA on an inexpensive SATA card makes much better sense.
| Quote: | If you need performance then the fast SATA disk plus adapter will be
more expensive than the fast SCSI disk.
|
Probably NOT but the SATA+adapter is a low performance solution. |
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Ron Reaugh
Guest
|
| Posted:
Thu Sep 23, 2004 1:12 am Post subject:
Re: SATA drive on SCSI bus |
|
|
"Ryo Kato" <ryo.news@gmx.de> wrote in message
news:2rd7guF1943ppU1@uni-berlin.de...
| Quote: | Keve Nagy <no_spam@poliod.hu> wrote:
I was wondering, what makes SCSI better than IDE/ATA/ATAPI/SATA.
Read any "scsi vs. ide"-related websites/documents/discussions of last 10
years.
|
And in all the recent ones the consensus is that SCSI has no advantage on
single user workstations. |
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Goran Larsson
Guest
|
| Posted:
Thu Sep 23, 2004 1:31 am Post subject:
Re: SATA drive on SCSI bus |
|
|
In article <USl4d.414446$OB3.369626@bgtnsc05-news.ops.worldnet.att.net>,
Ron Reaugh <rondashreaugh@att.net> wrote:
I trust what I can see for myself in the market much more
than I trust your narrowminded posts.
--
Göran Larsson http://www.mitt-eget.com/ |
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Ron Reaugh
Guest
|
| Posted:
Thu Sep 23, 2004 2:00 am Post subject:
Re: SATA drive on SCSI bus |
|
|
"Goran Larsson" <hoh@invalid.invalid> wrote in message
news:I4Gp4u.FJ5@approve.se...
| Quote: | In article <USl4d.414446$OB3.369626@bgtnsc05-news.ops.worldnet.att.net>,
Ron Reaugh <rondashreaugh@att.net> wrote:
NO!
I trust what I can see for myself in the market much more
than I trust your narrowminded posts.
|
None of that changes what folks who do actual research and find the truth
for themselves will see. |
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Folkert Rienstra
Guest
|
| Posted:
Thu Sep 23, 2004 2:43 am Post subject:
Re: SATA drive on SCSI bus |
|
|
"Keve Nagy" <no_spam@poliod.hu> wrote in message news:2rctbdF18cgqvU1@uni-berlin.de
| Quote: | Good Morning Newsgroup,
I was wondering, what makes SCSI better than IDE/ATA/ATAPI/SATA.
|
The application.
| Quote: | More precisely what I really wonder about is if the SCSI controller and
the bus alone (not including the devices) can make the difference in
range of raliability, speed and services.
|
Nothing much.
SCSI has a parity signal as an extra precaution against all data corruption
for which ATA has CRC but only for UDMA and only userdata transfers.
SATA is the ATA equivalent of Serial Attached Scsi (SAS).
SATA maybe just ATA with a serial convertor.
ATAPI is basically SCSI over ATA.
It cannot add something that isn't on the drive itself.
| Quote: |
As SATA drives are way cheaper than SCSI drives (compare a 160
or 200 GB drive for example),
|
But not available in 10k rpm.
| Quote: | this might be an interesting gadget.
|
All it does is convert the bus and add extra buffers and only those
features that are absolutely necessary to make the drive hehave so it
doesn't hold up the SCSI bus.
With not_native SATA drives you will be having convertor on top of
convertor.
| Quote: | So this brought up the question, what makes a real SCSI drive to be a
real SCSI drive?
|
The ability to be able to use sector sizes of your own choosing
and other tweakability that is not available on (S)ATA drives.
| Quote: | I am not a SCSI expert, I am only a SCSI user. I had experience with
different kinds of buses and I recognized that SCSI was the best for my
needs.
|
So what was the reasoning behind that?
| Quote: | Since then I mainly use SCSI.
This explains why I have these stupid questions. :-)
|
That depends on your previous reasoning.
| Quote: |
So, I wonder what relevant differences can be between a real (factory)
SCSI drive and a SATA drive connected to the SCSI bus using one of these
converters.
|
Mode pages that have a specific -not possible to emulate- purpose.
| Quote: |
I assume (only assume) that having a SATA disk and one of these converters
connected to my U160 SCSI bus and an Adaptec 29160 controller I can per-
form the same utilities I could on a factory SCSI disk, as these are provided
by the SCSI BIOS.
This means low level formatting,
|
Nope. No LLFormatting on (S)ATA drives.
Maybe. ATA doesn't have a verify command.
| Quote: | excluding tracks/sectors/cilinders, etc.
|
Nope.
| Quote: | AFAIK a SATA drive is capable of up to 150 Mb/s speed while an U160
SCSI is 160 Mb/s, so there should not be any significant performance
differences (again, in theory) comparing disks with similar
geometry, capacity and RPM.
|
Not true as SATA is point to point and SCSI is multidrop.
Relevant is that the SCSI interface side isn't slowing the host SCSI
bus down. Ultra160 SCSI drives usually are 30MB/s STR drives.
It is relevant though for cache reads and writes although the
convertor's internal buffers may obscure differences there too.
And depending on the application (like RAID) Ultra160 may be
too slow to sustain 4 SATA drives.
| Quote: | So, is there something I am missing here, is there something I should
take into account?
|
SCSI specific Features.
| Quote: |
The final task is to decide if it is worth to buy a SATA drive plus one
of these converters for about USD 110 instead of a more expensive
factory SCSI disk.
|
$110 buys you a nice SATA controller that supports 4 drives (or more).
| Quote: |
If you can help me in this decision or have any suggestion on this
topic, your comments and ideas are most welcome here.
Thanks,
Keve |
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Winey
Guest
|
| Posted:
Thu Sep 23, 2004 10:53 am Post subject:
Re: SATA drive on SCSI bus |
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|
On Thu, 23 Sep 2004 00:43:48 +0200, "Folkert Rienstra"
<see_reply-to@myweb.nl> wrote:
| Quote: |
"Keve Nagy" <no_spam@poliod.hu> wrote in message news:2rctbdF18cgqvU1@uni-berlin.de
Good Morning Newsgroup,
I was wondering, what makes SCSI better than IDE/ATA/ATAPI/SATA.
The application.
More precisely what I really wonder about is if the SCSI controller and
the bus alone (not including the devices) can make the difference in
range of raliability, speed and services.
Nothing much.
SCSI has a parity signal as an extra precaution against all data corruption
for which ATA has CRC but only for UDMA and only userdata transfers.
SATA is the ATA equivalent of Serial Attached Scsi (SAS).
|
A while ago I read a posting about SATA and SCSI that said, AFAIR,
that SAS would also allow attachment of SATA drives. Somehow. What
do you think?
| Quote: | SATA maybe just ATA with a serial convertor.
ATAPI is basically SCSI over ATA.
|
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Phil Barila
Guest
|
| Posted:
Thu Sep 23, 2004 11:00 am Post subject:
Re: SATA drive on SCSI bus |
|
|
"Keve Nagy" <no_spam@poliod.hu> wrote in message
news:2rctbdF18cgqvU1@uni-berlin.de...
[snip]
| Quote: | I assume (only assume) that having a SATA disk and one of these
converters connected to my U160 SCSI bus and an Adaptec 29160 controller
I can perform the same utilities I could on a factory SCSI disk, as
these are provided by the SCSI BIOS. This means low level formatting,
verifying, excluding tracks/sectors/cilinders, etc.
|
There is no truly analogous ATA command for most of the SCSI spec. That's
why most of the SCSI-ATA translators, whether they are bridge devices like
the one you mentioned, or software, like ATAPI.sys in Windows, implement a
command set that looks a lot like RBC.
Specifically, there is nothing at all like a FORMAT UNIT, the closest thing
to a verify is a READ VERIFY SECTORS. I'm not aware of any ATA command that
can exclude sectors, but that might be a consequence of composing this way
past when I should be asleep.
| Quote: | AFAIK a SATA drive is capable of up to 150 Mb/s speed while an U160 SCSI
is 160 Mb/s, so there should not be any significant performance
differences (again, in theory) comparing disks with similar geometry,
capacity and RPM.
So, is there something I am missing here, is there something I should
take into account?
|
Enterprise drives are specifically designed for 24/7 busy operation. ATA
drives typically aren't designed with that as the primary design goal.
| Quote: | The final task is to decide if it is worth to buy a SATA drive plus one
of these converters for about USD 110 instead of a more expensive
factory SCSI disk.
|
No, run SCSI disks on SCSI HBAs, or run SATA disks on SATA HBAs. The
exception to this would be a SATA (or PATA) RAID enclosure with a SCSI
interface. But that's all dependent on what your workload is.
Phil
--
Philip D. Barila Windows DDK MVP
Seagate Technology LLC
(720) 684-1842
As if I need to say it: Not speaking for Seagate.
E-mail address is pointed at a domain squatter. Use reply-to instead. |
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Keve Nagy
Guest
|
| Posted:
Thu Sep 23, 2004 2:43 pm Post subject:
Re: SATA drive on SCSI bus |
|
|
Thanks Guys very much!
You explained quite many useful things related to SCSI, ATA, ATAPI and
SATA that helps me understand these things better.
If anybody is interested, I made my final conclusion, which is that in
my case it is not worth buying such a converter. There could be only
very special circumstances very this converter turns out to be a
worthwhile and logical purchase.
I decided to stick to my SCSI only system, and without mixing the two,
maybe invest in a SATA controller and harddisk to see what that one can do.
Again, to all of you who replied, thanks very much for sharing your
opinion and knowledge on this topic with me! It definetly helped.
Keve
--
If you need to reply directly:
keve(at)mail(dot)poliod(dot)hu |
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Phil Barila
Guest
|
| Posted:
Fri Sep 24, 2004 9:33 am Post subject:
Re: SATA drive on SCSI bus |
|
|
"Winey" <NOSPAMME@no-one-here.com> wrote in message
news:8ls4l0p4i7b313ka1ruf3mpoiph6s4num4@4ax.com...
[snip]
| Quote: | A while ago I read a posting about SATA and SCSI that said, AFAIR,
that SAS would also allow attachment of SATA drives. Somehow. What
do you think?
|
SAS does indeed allow attachment of SATA devices. The converse isn't true,
you can't attach a SAS drive to a SATA HBA.
Phil
--
Philip D. Barila Windows DDK MVP
Seagate Technology LLC
(720) 684-1842
As if I need to say it: Not speaking for Seagate.
E-mail address is pointed at a domain squatter. Use reply-to instead. |
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