Slashdot Mirror
Western Digital Pulling Out Of SCSI HD Business
leiz writes "This article on Yahoo says Western Digital is pulling out of the enterprise hard drive business. This means they will no longer produce SCSI hard drives and Western Digital will be instead concentrating on the IDE and software business. What does this mean for the SCSI market? With 7200 rpm UltraATA/66 hard drives catching up in performance to SCSI HD, products such as the Fastrak RAID 0, 1, 0+1 card, and the cheap cost affectiveness of IDE/ATA, is SCSI no longer necessary for desktops / workstations / small servers?"
The current implementation of SCSI is 160 Mb/Sec. SCSI is a multitasking i/o subsystem (simultaneous read/write), IDE is not. SCSI typically impedes CPU performance by 3%, while IDE typically impedes CPU performance by ~25%. For Starters.
Come see Mr T teach CmdrTaco a lesson!
I pity the fool who don't like mr T!
Mr T vs Slashdot
Go Read it suckas!
Christ, I'm getting so incredibly sick of EIDE. First: A fast 7200 RPM drive will deliver no more than about 8-10 MB/s. Because of the brain-damaged nature of EIDE allowing only one device to talk at a time, anything beyond EIDE/16 has been useless dickwaving. Second: It's a creeping evil. Plextor has recently released an EIDE CD-R. My local Microcenter has completely stopped selling SCSI drives. They only stock Maxtor drives, as well. SCSI is no more expensive to produce then EIDE. IBM is at least good enough to not shaft people too for buying SCSI, and their UltraStar drives are the finest hard drives that can be had for love or money. But people will continue to buy crap, driving quality out of the market. Before too long, you won't be able to buy quality at all, or at least at anything approching a reasonable price.
I spent seven years at Western Digital, and I watched a chip company with an amazing amount of IP (basically everything except processor and memory) scuttle the chip business on the alter of the almighty hard drive. WD has seeded many successful companies in SoCal (Broadcom, QLogic, Emulex, Silicon Systems, Adaptec, JNI, more...) by letting go their talented engineers when management had failed yet again to follow in a market where they should have been leading. I'm sorry to have seen it happen yet again. Sounds like sour grapes, but it's really not; I'm just not surprised at this latest news. It's just another round of layoffs at WD, which isn't really anything new there. To any of the old guard still there -- you're a hardened lot, and I wish you luck in yet ANOTHER new direction set by the company. As for me, let's just say that in retrospect, WD was a great place to be from.
You don't use science to show that you're right, you use science to become right.
High end systems will be using SCSI for a bit.
1. ATA-66 can't touch 160 mb SCSI, even single drive to single drive, with serial access.
2. ATA performs very poorly when multiple reads and writes queue up.
3. SCSI handles large numbers (>4) drives much better, ATA sees problems with just 2 drives per channel.
Maybe ATA-262 will have a shot.
-Peter
Well, I'm a SCSI-only kinda guy myself, but there's a couple of points you glossed over...
4) SCSI has lower CPU overhead and doesn't make your system slug along as the kernel babysits the disk transfers.
Almost every bit of ATAPI kit out there these days uses DMA, which has made a big difference. It's not like the old days when you could see your CPU usage peak during a long copy operation. That said, SCSI still handles multiple requests better.
5) SCSI disks are usually made with higher MTBFs in mind.
True at one time, but many of the SCSI drives out there now are almost identical to their ATAPI counterparts, except for the interface.
WD always made bad SCSI drives, anyways. Their old ones, like ones were slow, noisy, and were heat problems. Their new ones were always considerably slow compared to their competition. WD was known for their IDE drives, but that reputation isn't to strong anymore.
I've got 4 SCSI one drives, a SCSI-2 Seagate Barracuda, a UW SCSI IBM (9zx), Yamaha CDRW.. my brother has two Seagate 4gb, and two Yamahas, and my mother has a SCSI caddy cdrom. And of course there's lots of IDEs laying around (hdds, cdroms, CDR, DVD), and a few MFMs, plus a prop. 1x sony cdrom.
Problems with SCSI:
1. Barracuda came defective. Same with Yamaha. Both from a really bad reseller who gave me a bad controller (defective), and claimed Seagate's tech. was lying and the drives really were out of production. Took 3 months to clear up.
2. IBM over heated, and eventually died months afterwards. IBM replaced within a week, the data was recoverable. The drive was 1st generation 10k rpm, and a pre-release w/ updated rom.
3. For some reason my brother's Yamaha CDR102 wont write onto newer cd media. Seems to be a cd-design change, as old media works fine.
4. Always requiring innovative tweaks to keep cool. SCSI caddy cdrom (6Plex) overheated and was replaced for free, years ago.
5. Pain to get UNIXes to install with the Yamaha. They'll boot off cd, and then say there's no CDROM to install from.
On non-SCSI problems:
1. Connar 1.4gb drive had bad blocks, years later stopped functioning.
2. 8x cdrom 'kinda' works.
3. 10/12x cdrom sticks.
So, there are more difficulties on SCSI, but cabling and installation is easier. Cooling is just a pain. Performance, though, is high. My Barracuda 2lp still outperforms IDEs in cpu/speed. The IBM is so fast I feel bad having it... Still, its amazing seeing 10% cpu used, max, when 100% is used on IDE, like the few DMA/33s I have.
SCSI for home = waste
SCSI for workstations = ok-good (mostly useful if the CAD is CPU oriented)
SCSI for servers = good-great (depends on what the server is doing, load, etc).
Just an anon that's really bored....
I've found the IDE performance problems go away entirely with the correct bus-mastering settings. You still can't get decent performance with two drives on a single channel, but my new Abit motherboard came with four IDE channels. So you can have four IDE hard drives without losing performance.
Here are some real benchmarks to back this up:
[root@olympus /root]# /sbin/hdparm -c0 -d0 -k1 -m0 -W0 /dev/hda /root]# /sbin/hdparm -t /dev/hda
/dev/hda: /root]# /sbin/hdparm -c1 -d1 -k1 -m16 -W1 /dev/hda /root]# /sbin/hdparm -t /dev/hda
/dev/hda:
<snip>
[root@olympus
Timing buffered disk reads: 64 MB in 28.40
seconds = 2.25 MB/sec
[root@olympus
<snip>
[root@olympus
Timing buffered disk reads: 64 MB in 4.86
seconds =13.17 MB/sec
That's with a 7200 Seagate drive. The first benchmark, giving a whopping 2.25MB/sec, was with all the IDE options in sucky mode. This is the way older IDE controllers work, and in large part responsible for IDE's bad name. The second benchmark shows that it can have good performance. It's CPU performance wasn't as good as SCSI's (17% out of 200%; dual-processor box) but wasn't as bad as many have said.
The big trouble with IDE is still that they are "dumb" devices that require CPU resources to manage. On workstations doing lots of disk access I can see NOTICABLE performance degradation between similar hardware, one of which is IDE, the other of which is SCSI. The nicest thing about SCSI is the fact that the controller offloads all disk management off of the system's CPU. If you're doing power computing, this makes a big difference. Also, as someone else mentioned, IDE has real problems allowing the system to manipulate multiple drives simultaneously, a problem SCSI does not have. For some schmuck just dicking around with Netscape so they can browse the web, who cares, but for hardcore users with big machines trying to get real work done, it can make a legitimate difference.
From a server perspective, there's no question that SCSI is the best. Just TRY putting more than four IDE drives into a Linux box without tearing your hair out and threatening to take a shotgun to the thing. The only way to do it is to get some sort of additional IDE controller like the Promise controllers which are unmitigated junk. I don't even want to mention the hoops I've gone through to to get a Promise Ultra33 stable in my Linux server. What makes it worse is that I could buy the four IDE drives I put in there for about the same price as I would have been able to pick up two SCSI drives of about the same size. (It's not that SCSI is so tremendously expensive as much as it is that IDE is just dirt cheap.) More unfortunately, I needed the space and I didn't have the extra money, or I *would* have just gone with SCSI. (As it turns out, I spent so much time trying to get the IDE drives working, I probably *should* have just gone SCSI from the get-go and saved myself money in the long run from doctor's bills from high blood pressure and ulcers trying to build an IDE-based server will give me.)
I see the whole "IDE vs. SCSI" thing as yet another case of mediocrity winning the battle. It doesn't have to be great as long as it's cheap and good enough to get the public to buy it. For those of us who like quality, we just have to pay so much more. Unfortunately, unlike the software industry, there's no way to start an "Open Source/Free Hardware" movement to force the other manufacturers to start focusing higher on quality.
-=-=-=-=-
-=-=-=-=-
My mom's going to kick you in the face!
Now that he's gone and the SCSI business is a memory, you can all expect nothing but crap to come out of this company for years to come.
All of these posters talking about EIDE (or whatever this months incarnation of the ATA spec is) being better than SCSI have no clue what they are talking about. I use my computers alot. Anytime I sit down to a system with any type of IDE drive, I can immediately feel the sluggishness set in, all while the CPU wastes cycles babysitting the rather braindead disk channel. Server or not, SCSI systems are *always* better and I will *always* continue to pay the extra quid to be at the keyboard of a system that doesn't slow me down. For me, that's not EIDE - ever.
Case in point: my shiny new Dell 600MHz system with the best Dell has to offer in EIDE technology. Many fingertip tappings waiting for the fluttering of the hard drive to settle down whilst I work. To me, that's not good technology or a good use of my time. At my earliest conveinance, I'll be swapping out the disc subsytem in favor of something with 80 pins and real bandwidth capability.
I certainly wouldn't use WD's for mission critical production servers.
I used to work at a computer company in the St. Louis, Mo area. We used WD drives exclusively. We got word that they had "oops"'d and that we have 30 to 50 IDE drives that we had to ship back to WD - AT OUR COST - even though it was thier defect. Needless to say, we switched to Fujitsu and never looked back, simply returning the drives and demanding a refund.
Hey Rob, Thanks for that tarball!
"Going to war without France is like going deer hunting without your accordion." - Jed Babbin
A lot of people use this EIDE crap, thinking it's great for a server and what not, after all it works for their desktop. It's not.
While I'll admit, there are some SCSI disks which are differentiated from the IDE drives solely by their interface, the higher end SCSI disks usually do have some serious advantages.
Some of the bigger SCSI advantages are
the fact of the matter is that if you want a cheap drive, you can buy a cheap EIDE drive, or a cheap SCSI drive. if you want a *good* drive, ultra-high quality EIDE drives are virtually non-existant, leaving you with good ole' SCSI.
A lot of people have this odd notion that when two computers are PIII 600s with 256 megs RAM and 18 gigs hard drive, but one costs $500 more, that the more expensive one is automatically a ripoff. People seem to forget that sometimes the more expensive one has better components and is less likely to die and wipe out the past two weeks of work. (all you non-student types, how much did you make in the past two weeks? I'd bet a *lot* more than $500). We need less ads that say the price, and more like the great VA Linux ad with the steak dinner on one page, and the TV dinner on the other.
I've got to say, this doesn't suprise me one bit.
I worked for a Computer Repair shop for about 5 months now. Here's the Breakdown on the Brand Names of Drives that come in Crashed that I've seen so far.
90% Western Digital - at least 20 that I can think of offhand
8% JTS (which are out of business) - 2 of these
2% Seagate - I know of 1 that had bad sectors
As of yet I've seen no Maxtor, Fujitsu, IBM, Quantum, Samsung or any other manufacture's hard drive crash. Although I've heard alot of bad things about the Maxtor Drives and the Quantum Bigfoot's Crashing. and I know from personal Experience that some old IBM Drives, (and I'm talking 10-15 year old PS/2 Hard Drives) were crap.
We would sometimes get WD drives that came fresh out of a box, stick it in a machine, and it would be damaged. My boss Had to deal with a company for a week because They bought a WD Enterprise Drive for their mission critial Server and it crashed. It Wasn't even a year old!
If I had a choice of any drive today, Hands Down I would have to go with the IBM Drive. If I had a second choice, I would probably go with a Samsung or a fujitsu.
In Soviet Russia, Trojan exploits YOU!
EIDE will eventually hit limits as even desktop computers become more demanding. As that time arrives SCSI will take over. On the server front, fibre channel is looking like the future over SCSI. It may be even more expensive but it is faster, has a crazy 10 km or so distance limit, supports more devices on one loop, and supports multiple HBA's connected to one set of devices. This allows multiple systems to talk directly to the storage rather than through a network to a computer that talks to the storage. SANs are going to really need fibre channel.
SCSI may seem to be "too much" for the average user but in that as the old MTV logo used to say..."Too much is never enough!" This held true for music television and it holds true for computers. I remember getting time on a 386 SX 25 Mhz with 4MB RAM and 80 MB hard disk. This was a $10,000+ system at the time. Now it's a paper weight for all but a few geeks (like me) who love to find uses for old hardware. I have a few IDE paper weights...I will have a few more before they are done.
-- soldack
Every engineer I've ever talked to at a HD co. has outright said that the IDE drives are not bui;t to anywhere near the quality levels that the same cos SCSI drives are. This for me is enough of a factor to go SCSI on anything that I want some reliability out of. IDE may be half price, but how much does it cost after a premature failure?
Most Linux setups I've seen default to using at least a couple of the "sucky" IDE controller settings. The "-d1" setting with hdparm is crucial, in particular, as it turns on DMA, which hacks a huge chunk out of your CPU usage, makes things nice for the scheduler, and increases transfer rates dramatically. With DMA off on my system MP3s skip whenever the hard drive thrashes too much; with DMA on I can't make an MP3 skip with any level of hard drive activity (and believe me I tried).
One last flag you might want to try: -X34 will make sure the drive is set to DMA mode 2 transfers, and on new drives -X66 will select Ultra DMA transfers. DMA->UDMA isn't nearly as big a leap as PIO->DMA, but it's sizable.
I wish more people knew about hdparm - it's a single command you can run as root that can double the performance of your system under some circumstances. I think new kernels are getting more aggressive about enabling good IDE settings themselves, but there are still too many systems out there where the default settings needlessly give both Linux and IDE a bad name.
IDE can't switch between master and slave fast enough to allow the greatest performance increases when striping with RAID and swap. It has silly limits like 2 drives per channel. It does'nt support command re-ordering in hardware to allow the heads to move less during many access'. It is not multi-threaded... blah blah blah. If this is true, I have lost respect for WD. My Caviar 340Mb is still going strong and I loved their build quality. I know IDE is getting really fast now, and it's cheap, but for the server with really disk heavy applications, transfer rate it not the be all and end all. Neither is how fast the heads can move. SCSI is far better for server stuff. Damnit!
War crimes, torture, lies, illegal spying... Would someone give Bush a blowjob, already, so he can be impeached?
Face it, the IDE design is ancient and is inadequate for today's uses. I mean its fine when you are plain ol' Joe Bob who just checks his email and does word processing. But when you want to *add* something to the computer and do some serious stuff, like a geek will, you're running into problems.
Not only does IDE have bad command queuing, it doesn't even do sync transfers. The most debated issue is the CPU usage and the transfer rate: IDE relies on the CPU more than it should because the controller is too simple and therefore braindead. You can overclock the IDE controller, but what always happens is the drive is too crappy to even handle the higher speed, but you always get the same read performance. IDE always sends date from devices back to the host controller at the same original spec speed, whereas write-to-device can vary due to oc'ing the controller.
Ok, now to the point:
the engineers (I'm sure they've been TOLD to do this) keep trying to make IDE "better" by keeping this backwards compatiblity junk and at the same time trying to squeeze a wider data bandwidth for the devices. Think about ATA/66, you need those special 80 wire/40 pin cables because if you used a regular 40 pin/wire cable the signal to noise ratio will be so bad that you get tons of CRC errors. The additional wiring are for the extra shielding in order to keep the SNR well enough to avoid CRC problems. What about adding additional devices for more storage space and removable like what most of us geeks do? Okay, they draw up these brilliant schemes of secondary, tertiary, and quarternary controllers which are essentially the same in controller design as the "primary" except on a different IRQ and port. Wow, cool, now I can hook up 8 IDE devices!
Ok, but I want to add some stuff like: a PCI soundcard (2 IRQs... 1 for ISA/DOS emu, and 1 for actual PCI), add NIC (there goes another IRQ), add DVD decoder card (1 IRQ). Hmmm... wait a minute, isn't IDE 0-3 using IRQ 10,11,14,15 already? So didn't that left me with IRQ 9 for video? Ok, suppose I _DON'T_ even have a NVidia based video card (which has problems sharing IRQs), and try to share IRQ 9 through "PCI steering" with the USB, also; that only gets me 2 devices working. I still have to disable the serial port(s), and the parallel port to get more of this working. It is possible to have one of the devices' IRQs share with the other, however this is all determined by the BIOS's DMI these days (in a modern PCI BIOS at least). I'm only talking about PCI here, ISA is already a forgotten issue since I'm talking about the latest and "greatest" motherboard.
Aren't they trying to keep some ancient inferior, simple interface up to date and competitive just because its "cheaper"? AFAIK, it should cost no more to make a SCSI device/drive with the *same* MTBF rating as an IDE device. IDE works, only when you are keeping things *simple*, but things aren't so simple these days. The more expensive, branded, prebuilt *gasp* systems these days already come with a decent sized HD, with DVD, and usually a burner, and sometimes a Zip or LS-120. This means 2 IDE channels may already taken up. IDE seems cost effective, but it doesn't look like it to me when it comes to long term. Its more trouble than its worth when you are going to add cards into your slots. Doesn't this remind you of the saying "beating a dead horse" to you?
It all comes down to this: we all know that we are in a serious IRQ resource problem already, and adding to that we get "newer and better" IDE "standards" which contributes to this problem even more. What I think should be done is to either ditch IDE (it worked great as a cheap solution but is no longer really viable), or take care of the IRQ problem. However, there is one thing that seem to be preventing this: the industry thinks they need to maintain backwards compatibility. I feel that there will eventually come a day where someone out there in some company will crack and actually officially acknowledge of this problem and is actually willing to deal with it.
My strongly suggested action is to actually make SCSI cheaper (man, they make tons of money selling those things, when costs of manf are no more than IDE), thus allowing IDE to be rid of, and in turn allow us to connect at least 15 devices (Wide SCSI) and using only 1 controller, 1 IRQ, 1 port, and lower CPU usage tremendously.
I still have to admit that IDE is ideal for people, and some of the geeks out there who are poor and can't afford good stuff like SCSI. But the minute you can afford and want to do serious (workstation/server) stuff, there is no doubt about it: SCSI is the way to go.
TheMAN
Here's a tip sent around our company concering tweaking IDE perf. Thanks to Andrew Tridgell for the info.
/dev/hda /dev/hdc
/dev/hda /dev/hdc /dev/hdc > /dev/null & /dev/hda /dev/hda /dev/hdc /dev/hda
This tip is useful for just about any Linux box, and is probably the
simplest way to significantly speed up your IDE based Linux box
without changing the hardware.
If you are impatient then just add the following near the top of your
/etc/rc.d/rc.sysinit (or equivalent startup script):
/sbin/hdparm -u 1 -d 1
/sbin/hdparm -u 1 -d 1
(and so on for any IDE devices in your system)
Now for a more complete explanation.
By default Linux uses extremely conservative settings for IDE. In
particular the default settings do two things that make IDE perform
really badly:
1) DMA is not used. That means all data coming to/from the hard disk
or cdrom is processed a byte at a time by the CPU. That is not very
efficient. With a fast processor that isn't doing anything else at
the time this can appear fast in simple minded benchmarks but it is
a big drain on CPU resources when you are actively using the
machine.
2) hardware interrupts are masked during IDE transfers. That means
that while a lump of data is being transferred to/from a IDE device
no other interrupts are processed. This includes interrupts from
other IDE devices, from network devices, from serial ports and from
mice. Your whole machine is effectively clagged up doing nothing
but waiting for a horrendously slow device to say "I'm done". Not
good.
If you want to see just how slow this is on your system then do the
following:
1) put a CDROM in the drive.
2) run the following commands:
hdparm -d 0 -u 0
hdparm -d 0 -u 0
cat
hdparm -t
hdparm -d 1 -u 1
hdparm -d 1 -u 1
hdparm -t
that shows you the hard disk speed while accessing the CDROM with the
default settings and with the improved settings. On my system the hard
disk speed goes from 3.8 MB/sec to 12.9 MB/sec. I've seen much bigger
changes on some other systems.
Even more importantly than the speedups is the fact that you will stop
dropping your PPP connection while doing cdrom transfers, and you will
be able to use your system while burning a cdrom without creating a
coaster.
You may wonder why the default settings are so poor. The reason is
that there is some rare hardware out there that corrupts data during
IDE transfers when you either use DMA or receive an interrupt during a
transfer. If that happens then the kernel should detect the failure
(in nearly every case) and fall back to the default
settings. Unfortunately after the auto-fallback you are still left
with corrupt data in your cache. Luckily systems that don't handle DMA
and unmasked interrupts are really quite rare these days so it is a
pretty safe bet to turn the options I suggested above, especially if
your system isn't from the stone age.
For more info and piles of options for fine tuning your IDE system try
"man hdparm".
7200rpm + U/ATA66 can sustain some wickedly fast speeds. For this reason I chose this on an Abit BE6 motherboard and cheap 7200rpm IDE drives for my cheap budget server at my cash strapped school.
I was astounded when I ran an hdparm -t (without cache disk speed test) and it reported 21MB/sec. This went well beyond my expectations from a little cheap IDE drive.
In situations where you only have one disk per controller (the Abit BE6 has two U/ATA 66 controllers), 7200rpm IDE can actually outperform SCSI based systems. (According to an article on Thresh's Firing Squad)
HOWEVER, SCSI still beats the heck out of IDE in reliability, speed and scalability in large and important jobs (enterprise solutions). The redundancy and failover protection of SCSI + raid controllers is not as reliable with IDE (it's possible with stupid human tricks). Don't even talk to me about software RAID. Software RAID is too CPU intensive. SCSI + RAID controllers can do all the failover, drive rebuilding and cool stuff without the CPU knowing anything about it.
Also, the extra bandwidth of SCSI shines when many hard disks are added to the fray. IDE has nowhere near the level of scalability of SCSI.
So basically, I highly suggest U/ATA 66 IDE for desktops, workstations and low budget servers. But for large and important jobs use SCSI.
I was reading the comments, getting angrier and angrier with the price difference between IDE & SCSI, when I thought this: 'I wonder if it would be possible to rip of the IDE controller board from a hard disk and replace it with a SCSI one'
Any thoughts?
-Yarn - Rio Karma: Excellent
Folks,
I think many of you are missing the point.
The big advantage of IDE is simple: low cost. Remember, in the old days you had to buy a separate hard disk controller, and that hogged valuable expansion slot space (not to mention the time wasted in doing a low-level format of a hard drive.)
Since IDE drives don't need a separate controller card (and don't need low-level formats), all you need to do in 1999 is connect the drive to the motherboard (heck, even the system BIOS will automatically set up the drive type), and you can right there install the operating system of your choice.
Also, in the past people have rightly criticized about IDE drive's low performance compared to SCSI drives. However, with Intel shipping the 82371 series of I/O controller chips, that allows software drivers to be written that dramatically reduce the CPU utilization to access an IDE drive. Also, the development of Programmed I/O Mode 4 in the early 1990's, ATA-33 in 1996 and ATA-66 in 1999 has dramatically increased throughput on IDE hard drives to the point that for most desktop operating systems there is almost nothing to be gained by going to SCSI hard drives.
The only place where SCSI hard drives still are useful are in environments where hard disk access is very heavy, such as in servers. This is where the RAID 5 capability of modern SCSI host adapters and the throughput of SCSI Ultra-Wide and Ultra2-Wide becomes useful.
It's small wonder why Western Digital is no longer interested in SCSI hard drives. That's because IDE hard drive technology has advanced to the point that SCSI hard drives are only useful for server environments.
Raymond in Mountain View, CA
SCSI Fanatic: I can burn 2 CDs while I play quake 3, do 24 bit colour scanning, leech mp3s and watch the latest pamela anderson vid.
IDE Fanatic: IDE is cheaper.
SCSI Fanatic: Oh yeah????? Well my drive rotates at 20,000 gigaschmirkels per second and I can chain ***37*** DRIVES TOGETHER!
IDE Fanatic: IDE is cheaper.
SCSI Fanatic: So, my mega-ultra-fat-wide-giga-fast-scsi-4 drive can do simultaneous reads and writes and can reorder requests fast enough to pilot the space shuttle - LETS SEE YOUR IDE DRIVE DO THAT!!!! AHHAAHAAHAAHHAHAHHHHAHAHAHAHHAHAHAHAHAHAHA AHAHAHAHAHAHAHHAHA AHAHAHAHAHAH AHA!
IDE Fanatic: IDE is cheaper.
Do you see what I am getting at? Nobody is saying IDE is technically better, yet all these wonderful SCSI fans are screaming until they turn blue in the face and the veins in their forehead start bulging out. Frankly it's disgusting.
Stop it.
I mean it.
I can still see your veins.
I wasn't joking.
Let's see - PCI 1.0 can do 132MBytes/sec. Now that does limit a system that can produce 160Mbyte/sec - but not to 66 as per UDMA.
;-)
Further, it isn't SCSI that limits the speed of the drives, but rather the speed off the platter. The drives will BURST at 160 for blocks of data at some fraction of the size of the drives buffer.
So - then lets put 5 drives on the channel and stripe the data (can you say RAID) and you have
a high performance channel that will saturate PCI.
UDMA can't keep up with that.
Oh - I'm not really an expert in the stuff. I've just designed disk controller chips and an Ultra 160 host adapter.
Summary - Horse Hocky!
Have you compiled your kernel today??
(original post was in the wrong place)
I've read a ton of stuff on the debate about SCSI vs IDE...and I've seen some people comment on how "SCSI
seems to last longer" and I've seen other people comment on how "SCSI can handle multiple requests
better"...but I must confess, it took an electrical enginneer to explain to me the reason that SCSI blows IDE away in
servers, and always will: Let's start with the fact that most SCSI & IDE drives are identical in the hardware, it's
the logic board that's usually different. Both the SCSI drive and the IDE drive have the same MTBF. Which
drive is going to fail first in a server? The IDE will, every time -- BECAUSE IT WORKS HARDER, and
RUNS MORE. SCSI's ability to get multiple packets of data means the moving parts of the drive don't have to
work as hard as the IDE drive, which is sending the head flying over the platter for every little bit. Result? Two
servers, same workload, one with an IDE drive, one with a SCSI, both drives have the same MTBF...but the
IDE drive is chugging away to exhaustion while the SCSI drive caches some of the data it needs and is not
working nearly as hard. This is why the speed debate is useless as applied to servers. In a desktop? Sure, IDE
has its advantages, and big speed is always nice. But in a server in a business environment with a heavy
workload, time is the value, and downtime costs -- and that IDE drive is GOING to fail because it's working
10 times as hard as the SCSI drive is to get the same data. Now, if someone can just explain why it costs so
much more. I am inclined to agree with the previous poster who said that the hard drive companies just milk
the "business market" but I have no real facts to base that on