🚀 go-pugleaf

"Dale \"Mad_Murdock\" White" <whiteda@home.com> writes:

> First, you really shouldn't cross post to so many different newsgroup.

> A comparison of SCSI and IDE can be rather long and drawn out depending out which
> phase of the technology your at with each. Instead, I'll just go over the highlights
> and let other who so desire dive into the gory details.
> 
> Typically SCSI has always been faster than IDE (Currently it's
> 160MB/s versus 100 MB/s), offered more devices than IDE (15 to 7)
> and had little impact on CPU usage (5% versus 75%). With new
> technologies like UDMA and the ability to add multiple IDE cards,
> you can now come pretty close to matching SCSI functions and
> performance.

for one drive, the 160MB/sec vs 100MB/sec is completely unimportant.
drive speed is limited by the rotation speed of the disk and the
density of the information.  the most any one drive can do is
60MB/sec -- and that's a SCSI 15krpm job.  the max for an IDE is about
50MB/sec.

besides, many tasks do not require the fastest linear streaming, but
seek plays an important role.

SCSI advantages
1) support more hard disks -- up to 15 disks on one ribbon cable.
   this is where the 160MB/sec helps you.
2) faster hard drives -- 10k and 15k rpm disks are only available in
   SCSI.  seek times are faster not only due to faster rotation, but
   also a quicker head arm.
3) better protocols such as tagged queuing and disconnect (which allow
   you to send commands to other drives even though one or more are busy)
4) external equipment.

the latest revision of IDE has a disconnect mode, but afaik very few
drives support it.  both IDE and SCSI use DMA/busmaster data transfer
and use little CPU time (the old PIO mode for IDE was a CPU hog but
no longer relevant).

of course IDE equipment is pretty good and it's much cheaper.

i'd get IDE if i figure on one or two hard disks and a cd-writer.  if
you want 3 or more disks, then go SCSI.

SCSI tends to better support a more multi-tasking style of usage.
thus for a busy server, SCSI can really be a win.

> SCSI also tends to be more expensive then IDE, partly because of it's advantages and
> partly because SCSI devices have a longer mean time between Failure\repair
> (MTBF\MTBR). SCSI cards are able to multi process, meaning they can carry out
> multiple I/O request at a time, IDE, I believe, is still serial based meaning I/O
> request line up. You also need an OS like Win NT/2000/Linux to be able to take
> advantage of Multi process I/Os
> 
> With a normal PC, you can have 4 IDE devices. With any SCSI card you can have at
> least 7 and with new cards 15 devices. SCSI pretty much always gives you external
> connectors (as you probably won't find many cases that support 15 devices) SCSI also
> tend to have the larger drives first, but it seems in the last year or so, IDEs are
> really screaming by.
> 
> SCSI allows you to go greater distances. Depending on the technologies in use, the
> SCSI devices could be from 6 meters to 25 meters from the PC. SCSI allows you to
> share SCSI Buses, which is used in the cluster world to allow 2 or more PCs to access
> the same disks or at least the same disks arrays.
> 
> Until recently, SCSI was the only technology that offered hardware RAID features.
> (RAID is a subject in itself) Though most home users have never had a real need for
> it, and the cost for a hardware raid controller is normally not worth the minimal
> benefits (again, for a average home user). SCSI controllers also tend to have fairly
> large amounts of cache (or memory) on them. Most standard controllers today have
> between 32 to 64 megs of ram, with the big boys have as much as a gig of ram., of
> course, the cost for a 64 meg SCSI RAID controller is around $1000-3000, depending on
> the technology it deploys.
> 
> SCSI is ideal in environments that needs fast large disks, performing heavy read and
> write request. For more home users, there is very little reason to go to SCSI because
> the cost is so much more than the gain, especially running in the Win9x world. But if
> you wanted to create a 400 Gig disks volume at the hardware level, then SCSI would be
> the perfect technology.
> 
> Again, this is just kinda of skimming the surface, and their are plenty of variables
> to this. If you really want to know more, I would start at www.Adaptec.com and do a
> few searches on SCSI vs. IDE and RAID. Plenty of reading.
> 
> HTH
> 
> Dale
> 
> 
> "Holy Smoke" <kissme@columbus.rr.com> wrote in message
> news:cNYj7.37727$Iq4.18664937@typhoon.columbus.rr.com...
> > Can you tell me the difference between them? what is their advantage, and
> > disadvantage?
> > what can scsi do that ide cant? (sorry, hehe, i need more info about scsi,
> > know enough of ide)
> >
> > X-Post?
> >
> >
> 
> 

-- 
J o h a n  K u l l s t a m
[kullstam@ne.mediaone.net]
sysengr