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Haines Brown
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 Posted: Sun Sep 21, 2008 7:31 pm Post subject: SCSI vs SATA hard disks |
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For many years I've been devoted to SCSI hard disks, but market trends
seem to suggest SCSI is dying out. If that the case, does my sticking
with SCSI any longer make sense?
Would a move to a SATA 3.0 Gb/s drive such as the Seagate Barracuda mean
that I will henceforth have to accept drive unreliability? I'm more
interested in reliability than top speed (or, obviously, even cost).
If I were to attach a SATA drive to my desktop machine, I'd be inclined
to do a cross install of linux to the new SATA drive from my running
SCSI drive. Any reason such a procedure would be problematic because of
the interface difference?
--
Haines Brown, KB1GRM |
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Hactar
Guest
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| Posted: Sun Sep 21, 2008 9:26 pm Post subject: Re: SCSI vs SATA hard disks |
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In article <87hc89bmfm.fsf@teufel.hartford-hwp.com>,
Haines Brown <brownh@teufel.hartford-hwp.com> wroteready worko), there
| Quote: |
Would a move to a SATA 3.0 Gb/s drive such as the Seagate Barracuda mean
that I will henceforth have to accept drive unreliability?
|
_All_ drives are unreliable to some degree. The ultimate in
computer-readable reliability is probably Tyvek punched tape.
| Quote: | If I were to attach a SATA drive to my desktop machine, I'd be inclined
to do a cross install of linux to the new SATA drive from my running
SCSI drive. Any reason such a procedure would be problematic because of
the interface difference?
|
Never had a SATA drive, but as long as your kernel has support _at boot
time_ for SATA and your controller (and fileystem but that already
work), there shouldn't be a problem. Make sure you copy the boot
blocks as well as the filesystem.
--
-eben QebWenE01R@vTerYizUonI.nOetP royalty.mine.nu:81
What do you do with dead chemists?
Barium. -- Harold_of_the_Rocks on Fark |
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Haines Brown
Guest
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| Posted: Sun Sep 21, 2008 10:50 pm Post subject: Re: SCSI vs SATA hard disks |
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ebenZEROONE@verizon.net (Hactar) writes:
| Quote: | In article <87hc89bmfm.fsf@teufel.hartford-hwp.com>,
Haines Brown <brownh@teufel.hartford-hwp.com> wroteready worko), there
Would a move to a SATA 3.0 Gb/s drive such as the Seagate Barracuda mean
that I will henceforth have to accept drive unreliability?
_All_ drives are unreliable to some degree. The ultimate in
computer-readable reliability is probably Tyvek punched tape.
|
Yes, but my subjective impression is that there is a very wide
difference in reliability. Of the dozen SCSI drives I've used over the
years, only one failed on me; reading on line discussions and reviews,
it seems that SATA drives fail regularly.
I guess my question comes down to, why should one bother these days with
the added expense of SCSI hard disks?
| Quote: | If I were to attach a SATA drive to my desktop machine, I'd be inclined
to do a cross install of linux to the new SATA drive from my running
SCSI drive. Any reason such a procedure would be problematic because of
the interface difference?
Never had a SATA drive, but as long as your kernel has support _at boot
time_ for SATA and your controller (and fileystem but that already
work), there shouldn't be a problem. Make sure you copy the boot
blocks as well as the filesystem.
|
A chroot cross install is complicated, but I've gotten used to it, and
it ensures the kind of control I want and an installation that does not
interrupt using my current drive for work I assume that the kernels now
out all support SATA, and boot blocks are no problem as long as one sets
the file system up properly.
--
Haines Brown, KB1GRM |
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Hactar
Guest
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| Posted: Mon Sep 22, 2008 12:19 am Post subject: Re: SCSI vs SATA hard disks |
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In article <87d4ixbd77.fsf@teufel.hartford-hwp.com>,
Haines Brown <brownh@teufel.hartford-hwp.com> wrote:
| Quote: | ebenZEROONE@verizon.net (Hactar) writes:
In article <87hc89bmfm.fsf@teufel.hartford-hwp.com>,
Haines Brown <brownh@teufel.hartford-hwp.com> wroteready worko), there
Would a move to a SATA 3.0 Gb/s drive such as the Seagate Barracuda mean
that I will henceforth have to accept drive unreliability?
_All_ drives are unreliable to some degree. The ultimate in
computer-readable reliability is probably Tyvek punched tape.
Yes, but my subjective impression is that there is a very wide
difference in reliability. Of the dozen SCSI drives I've used over the
years, only one failed on me; reading on line discussions and reviews,
it seems that SATA drives fail regularly.
I guess my question comes down to, why should one bother these days with
the added expense of SCSI hard disks?
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It is my impression (which may be false and/or out of date) that the
instances of drive hardware that are matched with SCSI controllers are the
more reliable (longer-lasting) ones.
| Quote: | If I were to attach a SATA drive to my desktop machine, I'd be inclined
to do a cross install of linux to the new SATA drive from my running
SCSI drive. Any reason such a procedure would be problematic because of
the interface difference?
Never had a SATA drive, but as long as your kernel has support _at boot
time_ for SATA and your controller (and fileystem but that already
work), there shouldn't be a problem. Make sure you copy the boot
blocks as well as the filesystem.
A chroot cross install is complicated, but I've gotten used to it, and
it ensures the kind of control I want and an installation that does not
interrupt using my current drive for work I assume that the kernels now
out all support SATA, and boot blocks are no problem as long as one sets
the file system up properly.
|
I was thinking of taking your existing installation and copying it over
(that's what I've always done except PATA -> PATA), but whatever floats
your boat.
--
-eben QebWenE01R@vTerYizUonI.nOetP royalty.mine.nu:81
Hi! I'm a .sig virus! Copy me to your .sig! |
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noi ance
Guest
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| Posted: Mon Sep 22, 2008 12:29 am Post subject: Re: SCSI vs SATA hard disks |
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On Sun, 21 Sep 2008 10:31:09 -0400, Haines Brown typed this message:
| Quote: | For many years I've been devoted to SCSI hard disks, but market trends
seem to suggest SCSI is dying out. If that the case, does my sticking
with SCSI any longer make sense?
|
IMO, for the cost of a 74GB SCSI drive, you could probably buy a 300GB
SATA, or a 300GB SCSI 2-300GB SATA for a RAID configuration. BTW, get
newer 5,400rpm SATA for quieter cooler operation.
| Quote: | Would a move to a SATA 3.0 Gb/s drive such as the Seagate Barracuda mean
that I will henceforth have to accept drive unreliability? I'm more
interested in reliability than top speed (or, obviously, even cost).
|
All drives are unreliable to some extent thats why they came up with
RAID. Make sure your SATA device supports RAID 1 or RAID 5.
| Quote: | If I were to attach a SATA drive to my desktop machine, I'd be inclined
to do a cross install of linux to the new SATA drive from my running
SCSI drive. Any reason such a procedure would be problematic because of
the interface difference?
|
Not sure how that's going to work.
If your PC recognizes both the SCSI and SATA; and can boot either that's
step one. Then if you're running LVM you can get a migraine by adding
the SATA drives as a new LVG and transfer data. Don't know about making
the SATA VG the boot over the SCSI VG.
If you're not running the LVM then the format, partition the SATAs, dd
the SCSI stuff to the SATA drives, modify the fstab and grub to point to
the SATA drives, change bios to boot the SATA drives first. |
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Rikishi42
Guest
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| Posted: Mon Sep 22, 2008 3:15 am Post subject: Re: SCSI vs SATA hard disks |
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On 2008-09-21, Haines Brown <brownh@teufel.hartford-hwp.com> wrote:
| Quote: | For many years I've been devoted to SCSI hard disks, but market trends
seem to suggest SCSI is dying out. If that the case, does my sticking
with SCSI any longer make sense?
|
It hardly never did, sorry. SCSI is only the interface. There have been
drives that were sold with eighter SCSI or IDE interfaces, but were
otherwise identical.
| Quote: | Would a move to a SATA 3.0 Gb/s drive such as the Seagate Barracuda mean
that I will henceforth have to accept drive unreliability? I'm more
interested in reliability than top speed (or, obviously, even cost).
|
The notion that SCSI drives are inherently more reliable has been a very
irritating myth for well over 20 years now. Most observations of SCSI
reliability fail to include a more complete picture of the situation.
These are just examples I can come up with now:
1. Drive speed: SCSI's are usually slower drives. Less mechanical stress,
less heat stress. Older, more reliable technology.
Solution: buy a slow IDE/SATA.
2. Drive capacity: SCSI's are usually smaller. The bigger the disk, the
closer to the cutting edge, therefore the less reliable.
Solution: buy smaller disks.
3. Drive usage: SCSI's are mostly used in servers. Think constant operation.
Compare with the frequent on/off switching of personal desktops or laptops.
Guess where disks suffer most.
Solution: keep the machine running, including giving it a UPS.
To me, there is a _potential_ reason that SCSI's used to be more reliable.
HD production could have quality control. You could argue that a batch of
drives that turns out to be of higher quality, would be set aside to get
SCSI electronics. The clients buying SCSI are prepared to pay more, so those
drives could be sold with more profit. But where I would have believe such a
scenario even 10 years ago, I don't trust manufactors to put that much
effort in such checks/selections anymore.
| Quote: | If I were to attach a SATA drive to my desktop machine, I'd be inclined
to do a cross install of linux to the new SATA drive from my running
SCSI drive. Any reason such a procedure would be problematic because of
the interface difference?
|
No, why? If by installing, you mean setting up the OS from scratch. Which
includes selecting drivers. The detection process will select SATA rather
then SCSI modules. The source disk is not important, as long as it's
complete. Depends on your distro and how's it's installed, really. You
should provide a bit more details on your configuration.
--
Elevators smell different to midgets |
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Sheridan Hutchinson
Guest
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| Posted: Mon Sep 22, 2008 3:34 am Post subject: Re: SCSI vs SATA hard disks |
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Haines Brown wrote:
| Quote: | If I were to attach a SATA drive to my desktop machine, I'd be inclined
to do a cross install of linux to the new SATA drive from my running
SCSI drive. Any reason such a procedure would be problematic because of
the interface difference?
|
If by cross-install you mean 'disk clone', then this very workable.
I heard on the grape-vine that some folks are preparing some machines in
VirtualBoxes and then later copying them across to the production
machines when they're happy with the core configuration.
If you're using an LVM you might have complications but it's worth a go
to see what happens.
Before you clone install a stock kernel, the ones in Debian at least are
stacked with multiple drivers to get your system up an running,
presumably other distros are the same or very similar in this regard.
G4l is one opensource option for disk cloning, or you could use gparted,
or you could use Acronis TrueImage (a closed source commercial option,
by it is reliable). All of these solutions can resize the new
partition(s) on to the new disk as you'd like them.
--
Regards,
Sheridan Hutchinson
Sheridan@Shezza.org |
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Aragorn
Guest
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| Posted: Mon Sep 22, 2008 5:57 am Post subject: Re: SCSI vs SATA hard disks |
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On Sunday 21 September 2008 16:31, someone identifying as *Haines Brown*
wrote in /comp.os.linux.hardware:/
| Quote: | For many years I've been devoted to SCSI hard disks, but market trends
seem to suggest SCSI is dying out. If that the case, does my sticking
with SCSI any longer make sense?
|
I'm not so sure that's a market trend. It just so happens to be that SCSI
is no longer considered useful in the home and office desktop market, but
servers are most definitely still using SCSI.
However, the SCSI that's being used and marketed today is no longer of the
parallel variant. Just as parallel ATA had to make way for serial ATA,
SCSI has by now already started making way for serial attached SCSI (SAS)
and iSCSI for storage area networks.
The big advantage of SAS is that SAS controllers can be used both with SAS
disks *and* SATA disks, intermixed - note: you cannot connect an SAS disk
to an SATA controller, though! - and the current bus speed for each
individual disk is 3.0 Gbit/sec, or 384 MB/sec. The new SAS standard will
be twice that fast.
| Quote: | Would a move to a SATA 3.0 Gb/s drive such as the Seagate Barracuda mean
that I will henceforth have to accept drive unreliability? I'm more
interested in reliability than top speed (or, obviously, even cost).
|
I'm not too familiar with brandnames and types, but I believe the Barracuda
is an enterprise-grade disk. Western Digital also have a number of
enterprise-class SATA disks out, and these are all intended for 24/7 usage.
Of course, SCSI and SAS have better error checking and correcting, which
SATA does not have - at least, not to my knowledge - and so if absolute
reliability is your priority, then SAS would be the best choice. SAS disks
also tend to perform slightly better than SATA because of TCQ versus NCQ.
But of course, the difference in price per unit of storage capacity between
SAS and SATA is huge, and ultimately it's your call. I myself actually
have a machine here with a SAS RAID 5, comprised of 4 SAS disks.
| Quote: | If I were to attach a SATA drive to my desktop machine, I'd be inclined
to do a cross install of linux to the new SATA drive from my running
SCSI drive. Any reason such a procedure would be problematic because of
the interface difference?
|
No, but you must of course keep in mind that the kernel on the target disk
has support for that disk's controller. So if you're using a custom-built
kernel and you've left out SATA support, you'll have to make sure that you
recompile the kernel and include SATA support before you copy the lot
over. ;-)
--
*Aragorn*
(registered GNU/Linux user #223157) |
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Matthew Wild
Guest
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| Posted: Mon Sep 22, 2008 2:06 pm Post subject: Re: SCSI vs SATA hard disks |
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Rikishi42 wrote:
| Quote: | On 2008-09-21, Haines Brown <brownh@teufel.hartford-hwp.com> wrote:
For many years I've been devoted to SCSI hard disks, but market trends
seem to suggest SCSI is dying out. If that the case, does my sticking
with SCSI any longer make sense?
It hardly never did, sorry. SCSI is only the interface. There have been
drives that were sold with eighter SCSI or IDE interfaces, but were
otherwise identical.
Would a move to a SATA 3.0 Gb/s drive such as the Seagate Barracuda mean
that I will henceforth have to accept drive unreliability? I'm more
interested in reliability than top speed (or, obviously, even cost).
The notion that SCSI drives are inherently more reliable has been a very
irritating myth for well over 20 years now. Most observations of SCSI
reliability fail to include a more complete picture of the situation.
These are just examples I can come up with now:
1. Drive speed: SCSI's are usually slower drives. Less mechanical stress,
less heat stress. Older, more reliable technology.
Solution: buy a slow IDE/SATA.
I'd take issue with this one. All the SCSI disks we've got or worked |
with over the last 10-12 years have been 10K or 15K. All the SATA/IDE
disks are 7.2K, or 5.4K for laptops.
| Quote: | 2. Drive capacity: SCSI's are usually smaller. The bigger the disk, the
closer to the cutting edge, therefore the less reliable.
Solution: buy smaller disks.
3. Drive usage: SCSI's are mostly used in servers. Think constant operation.
Compare with the frequent on/off switching of personal desktops or laptops.
Guess where disks suffer most.
Solution: keep the machine running, including giving it a UPS.
To me, there is a _potential_ reason that SCSI's used to be more reliable.
HD production could have quality control. You could argue that a batch of
drives that turns out to be of higher quality, would be set aside to get
SCSI electronics. The clients buying SCSI are prepared to pay more, so those
drives could be sold with more profit. But where I would have believe such a
scenario even 10 years ago, I don't trust manufactors to put that much
effort in such checks/selections anymore.
I think they did more qualification of SCSI disks, because they are most |
likely to be sold into an enterprise environment which wants better
guarantees. I'd agree that there aren't any real differences between
SCSI and SATA drives now, GB for GB.
Matthew |
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Pascal Hambourg
Guest
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| Posted: Mon Sep 22, 2008 3:23 pm Post subject: Re: SCSI vs SATA hard disks |
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Hello,
Aragorn a écrit :
| Quote: |
The big advantage of SAS is that SAS controllers can be used both with SAS
disks *and* SATA disks, intermixed - note: you cannot connect an SAS disk
to an SATA controller, though! - and the current bus speed for each
individual disk is 3.0 Gbit/sec, or 384 MB/sec.
|
I don't know about SAS, but the SATA bus speed with 3 Gbit/s (i.e.
3*10^9, not 3*2^30) signalling rate is 300 MB/s, not 384. Each 8-bit
data byte is transmitted as a 10-bit pattern on the wire. |
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Douglas O'Neal
Guest
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| Posted: Mon Sep 22, 2008 6:00 pm Post subject: Re: SCSI vs SATA hard disks |
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On 09/21/2008 10:31 AM, Haines Brown wrote:
| Quote: | For many years I've been devoted to SCSI hard disks, but market trends
seem to suggest SCSI is dying out. If that the case, does my sticking
with SCSI any longer make sense?
Would a move to a SATA 3.0 Gb/s drive such as the Seagate Barracuda mean
that I will henceforth have to accept drive unreliability? I'm more
interested in reliability than top speed (or, obviously, even cost).
If I were to attach a SATA drive to my desktop machine, I'd be inclined
to do a cross install of linux to the new SATA drive from my running
SCSI drive. Any reason such a procedure would be problematic because of
the interface difference?
|
Particularly in light of some of the comments that have already been made,
you might find
http://www.usenix.org/publications/login/2006-06/openpdfs/chan.pdf
interesting reading. The author is a technical director at NetApp so the
bias might be more apparent than in other posts, but the comparisons between
drive types looks solid.
Doug |
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Chris Cox
Guest
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| Posted: Mon Sep 22, 2008 9:00 pm Post subject: Re: SCSI vs SATA hard disks |
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Haines Brown wrote:
| Quote: | For many years I've been devoted to SCSI hard disks, but market trends
seem to suggest SCSI is dying out. If that the case, does my sticking
with SCSI any longer make sense?
|
SCSI has been replaced by SAS. So.... going forward, no, SCSI is
definitely a bad choice. However, SCSI drives and HBAs will be around
for some time. But the future belongs to SAS. Most all SAS
implementations now can also tunnel SATA, so you can usually
do both, but there can be a difference if using a hotswap
backplane.
Future right now = SAS and SATA
| Quote: |
Would a move to a SATA 3.0 Gb/s drive such as the Seagate Barracuda mean
that I will henceforth have to accept drive unreliability? I'm more
interested in reliability than top speed (or, obviously, even cost).
|
Drive reliability is an issue regardless of type. However, consumer
based SATA drives do not have to pass as rigorous set of test as
SAS (and SCSI) drives do. The exception is the enterprise level
SATAs which are usually target for high end storage... also alot
of the Raptors are VERY similar to their SAS/SCSI cousins. But Seagate
is a very mixed bag right now with some of their drives produced
by the same fab as the Maxtor (very cheap) drives. So some Seagates,
especially on the OEM side will fail within a year (sad but true
from my own experience). I don't think it's wise to say which
vendor is "good" or "bad"... they are all one big roller coaster
of reliability. Right now, my WD drives are holding up well and
my enterprise side Hitachi's. Drives I hate include Maxtor and
Seagate.... buy YMMV.
| Quote: |
If I were to attach a SATA drive to my desktop machine, I'd be inclined
to do a cross install of linux to the new SATA drive from my running
SCSI drive. Any reason such a procedure would be problematic because of
the interface difference?
|
Probably not. There are a few (very few) SATA controllers that cause
problems for Linux. Sometimes it's a BIOS issue where some will let
you change things to work with Linux and others won't. But it's only
on a small set of machines. I'd say I've seen the most problems with
HP's consumer line. The are pretty Linux unfriendly.... even their
business workstation/laptop line isn't particularly Linux friendly.
HP does a good job on the server side though.
If you have a working SATA, there shouldn't be a problem making
the copy... but because of drive ordering issues, you may have to
make some post copy adjustments to grub (in particular) and possibly
your initrd so that ordering is either changed, or things are adjust
to switch the drive ordering using a combination of grub and/or the
bios to match things up correctly (not quite sure that "cross install"
means in your context).
It's all pretty repairable, but certainly not an easy process
for a newbie to tackle. Too may variables to reliably document
with some kind of "silver bullet" formula. |
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Aragorn
Guest
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| Posted: Tue Sep 23, 2008 12:04 am Post subject: Re: SCSI vs SATA hard disks |
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On Monday 22 September 2008 12:23, someone identifying as *Pascal Hambourg*
wrote in /comp.os.linux.hardware:/
| Quote: | Aragorn a écrit :
The big advantage of SAS is that SAS controllers can be used both with
SAS disks *and* SATA disks, intermixed - note: you cannot connect an SAS
disk to an SATA controller, though! - and the current bus speed for each
individual disk is 3.0 Gbit/sec, or 384 MB/sec.
I don't know about SAS, but the SATA bus speed with 3 Gbit/s (i.e.
3*10^9, not 3*2^30) signalling rate is 300 MB/s, not 384. Each 8-bit
data byte is transmitted as a 10-bit pattern on the wire.
|
Well, I had read that it was 384 MB/sec for SAS and 300 MB/sec for SATA -
given that SCSI data and commands are both transmitted in 32 bit units from
U320 up - but either way, even 300 MB/sec by far exceeds the real
throughput capacity of a single hard disk, and with both SAS and SATA, the
available bus speed applies to each individual storage device, as opposed
to for the total of devices connected to the controller as in the case with
parallel SCSI or ATA. ;-)
--
*Aragorn*
(registered GNU/Linux user #223157) |
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Haines Brown
Guest
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| Posted: Tue Sep 23, 2008 1:41 am Post subject: Re: SCSI vs SATA hard disks |
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Since you are puzzled by what I meant by cross-installation, let me be
more specific, although this is a simplified description.
1. Do a cfdisk on the newly attached hard disk (SATA or SAS). For
example, # cfdisk /dev/sdc, to create my partitions.
2. Initialize these partitions: # mk2fs /dev/sdc.
3. I make my first partition at least 500 Mb so that I can do a base
installation in it using cdebootstrap. I mount this installation
partition on /mnt/debinst and run something like:
# /usr/bin/cdebootstrap -v --arch i386 lenny /mnt/debinst
http://http.us.debian.org/debian
4. To configure base system, I chroot to the installation partition:
# chroot /mnt/debinst /bin/bash
Create a primitive fstab on the target disk so that I can mount broken
out partitions for moving directories out of the install directory.
5. Chroot to do a dpkg-reconfigure, etc.
--
Haines Brown, KB1GRM |
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Haines Brown
Guest
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| Posted: Tue Sep 23, 2008 1:45 am Post subject: Re: SCSI vs SATA hard disks |
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Your remarks on SCSI much appreciated. I find the SAS choices rather
expensive, and so probably will end up with SATA.
I run my machine 24/7, and normally only reboot every few months to do
something with hardware. That should reduce the stress on the drive and
help it survive for a while.
--
Haines Brown, KB1GRM |
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