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LVD SCSI vs CF/ATA

twolazy

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Building a pentium pro system and I have a few options...
Motherboard is an Intel PR440FX (dual 200/256) so nothing fancy but have 2 IBM/Plextor lvd drives attached. I have a couple SCA drives but all 7.2k atm.

Is it worth it to find 15k drives or should I just use IDE with CF cards? The drives dont matter to me to be quite honest. Main will be a 30gb kingston sata ssd with a sata to ide backplane. Its more just raw performance that I am after. Prices are similar for sizes (32 gb)... on fleabay. Downside of this motherboard is cant use any addon cards with roms. It refuses to boot any rom not integrated. Another downside is SCA drives need a backplane adapter to LVD.

Stuck with built in Adaptec 160uw or Intel ATA 33. Which way would any of you go, any advice or wisdom is welcome.
 
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Unknown_K

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My PR440FX was upgraded to dual 333 overdrives but I cannot remember what I have for a HD in it. Most likely I have some 68 pin SCSI as a boot drive running Win2k. I remember around 2000 or so when it was still a dual 200 machine having a PCI ATA100/133 RAID card and 2 x 60GB IDE drives striped and thinking it was fast.

SCA drives just need an adapter to 68 pin plus a SCSI cable that has a terminator on the end making life easy and probably faster then anything you put on the ATA 33 IDE port.

https://www.ebay.com/itm/265575718055

https://www.ebay.com/itm/283908343290
 

Eudimorphodon

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Its more just raw performance that I am after.

Then it's either the SCSI controller, or plugging something more modern into the PCI slot. The built-in IDE on a PR440FX motherboard is a PIIX3 bridge chip, and that's not even ATA33, the best it does is PIO Mode 4. (It may do UDMA mode 0 with the right drivers, maybe, but I'm not even sure it can manage that?) These old IDE chipsets tend to suffer from interrupt saturation before they can even really max out the 16MB/s or so they're theoretically capable of, so the only category where it's *possible* a flash drive connected to the IDE port would beat something connected to the SCSI adapter would be in random access time. (And even there you probably wouldn't with a CF card, you'll need a better SSD on a well-designed PATA bridge.)
 

mR_Slug

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I tend to go with SCSI, as it's period correct. Max you can get on ATA-33 is 33MB/s? so with SCSI it just comes down to the drives internal transfer rate. Sure you can find a late drive that is faster. Remember often the 10 and 15K drives need some good cooling. They are noisy too.
 

Eudimorphodon

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I messed around with IDE on the 440FX/PIIX3 a bit. It can saturate 16MB/s in XP at least

I have bad memories of that chipset being a dog, but I know in part it’s because for a while Linux distributions would often default to extremely conservative tuning settings and the resulting performance was dreadful if you neglected to change it. (I think the stated excuse was that some motherboards were buggy and better safe than sorry.)

In any case the SCSI controller should still in theory at least be both faster and more efficient, but only if you truly find drives up to the task.

Depending on what OS is desired here an option might be to stick some kind of sluggish CF-type adapter on the IDE port to hold the boot partition and use a PCI SATA card for main storage.
 

GiGaBiTe

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I'd say go with SCSI as well, either real SCSI or if you can find a SCSI to IDE adapter to use solid state storage like a CF or SD card.

IDE in PIO mode eats tons of CPU time, especially in the faster transfer modes. System performance will drag when disk activity is going on.
 

twolazy

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I am going to go with some 15k SCA drives, after thinking about it. I have a few UW 7200 drives I can use in the meantime till the 68pin UW to 80pin SCA backplanes come in. Only have one, so ordered 2 more.

Any recommendations on brand? Seagate?

EDIT: Looking at 146/144gb drives.
 
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twolazy

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So finally received my 80 pin SCA to 68 pin UW adapters, and dug out an older Seagate Hawk SCA drive. The results are , well lets say, rather disappointing. Perhaps this first gen SCA drive is slow, but I would have figured it be faster then PIO mode 2 with a 20 gb Hitachi IDE drive...

On the lookout I guess for a nice 15k drive. Noticing capacity is kinda overpriced after 36/37gb drives. What drives with those with experience with this area, suggest ? Theres no way this should be slower..
 

GiGaBiTe

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SCA is a hardware connector, it's not a SCSI speed standard. There are a variety of drives using different SCSI standards that use the SCA-80 backplane connector. The maximum speed you can get out of the drive relies on both the SCSI standard the drive uses, and the SCSI host controller supports.

If you have something like an Ultra 160 or 320 drive on an old 8 bit SCSI or even Fast SCSI host adapter, the drive is going to be crippled down to that slower speed.

Also note that faster spindle speeds does not equate more drive throughput. 10-15k RPM drives are more for lower latency than they are for increased throughput. While they may say something like Ultra 160 or 320, which means the SCSI bus can sustain that number in throughput, it does not mean the drives will get anywhere near that number. It's the same for mechanical drives on any interface, modern mechanical hard drives still don't saturate SATA-3 links except for data stored in the controller cache.
 

twolazy

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Oh I agree, wasn't expecting a single drive to saturate the controller, but I WAS expecting more then 4mb/s reg / 5mb/s burst speeds. Seems slow to me. That crappy 20gb Hitachi was getting 13 reg / 15 burst. Just seems off. Even the latency and seek times were 2-3x worse. Was not expected. In any case ordered a cheap HP 10k 36gb drive with a sled, should be here Thursday. Will try testing again. Perhaps that old Seagate Hawk is just older then I expected. I seem to recall Ultra Wide coming out in the 486 era, so perhaps I was expecting too much from the old drive.

Testing was done on an Adaptec 2940uw with bus mastering on. Believe its 40mb/s? tops?
 

GiGaBiTe

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The AHA-2940UW can only do 40 MB/s if the drive supports the "Ultra Wide SCSI" specification, which wasn't really a specification. SCSI standards were moving at lightning speed at the end of the 90s, sort of like how Wifi is moving now, where a pile of manufacturers are all trying to one up each other with vendor specific features. It resulted in a mess of quasi-compatible SCSI standards that could generally operate together, but at a lower compatible speed that they all supported.

Ultra Wide SCSI falls into the domain of SCSI-3 devices, which had interface speeds between 20 and 40 MB/s, but like with SATA III drives, the interface speed doesn't dictate the device speed.

I've personally never seen one of my 2940UW cards get anywhere near 40 MB/s unless I was using an Ultra 80, 160 or 320 drive. In most cases I only ever saw between 5-20 MB/s. It could be slower if the PCI bus was saturated.
 

Eudimorphodon

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Exactly what model Seagate Hawk have you been testing? The “Hawk” name went on some really bottom of the barrel drives, like the stock drives included in low-end Sparcstations like the 4. Not all SCSI drives are fast, by any stretch.
 

twolazy

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Seagate Hawk ST31230WC. Wow I thought it be a 7200RPM, its 5400 and not even SCSI 3 (specs say SCSI 2!), yet 80 pin?



I've personally never seen one of my 2940UW cards get anywhere near 40 MB/s unless I was using an Ultra 80, 160 or 320 drive. In most cases I only ever saw between 5-20 MB/s. It could be slower if the PCI bus was saturated.

Good to know actually. I was hoping it be faster then the PIO mode 4 supposedly the board supports, but can only seem to get PIO mode 2. Grrr. Wish it boot off any SATA / IDE cards I own. It just plain refuses to even see any cards bios, most likely due to its embedded SCSI controller. Work fine in windows most part. Just annoying.

Do have that HP ultra 160 drive coming... Would like to see it at least be faster then a 20gb Hitachi deathstar. Was going to use it as a vintage server for all my pre xp machines, macs whatnot. I do have a dual p4 xeon I guess I could use if this doesnt pan out way I hoped.

If it doesnt pan out, well I have 2 low hour PR440FX motherboards and 2 CPU's for sale, with all the accessories. (ram / cpu cooler / dual cpu vrms etc). LOL.
 
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Eudimorphodon

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Seagate Hawk ST31230WC. Wow I thought it be a 7200RPM, its 5400 and not even SCSI 3 (specs say SCSI 2!), yet 80 pin?

Oh, no, that’s an utter dog.

I guess if you’re only familiar with PC hardware it’s easy to assume that all SCA hard drives were high-performance server grade stuff, since that’s the role they served in the PC world, but there were plenty of, well, humble applications for the interface elsewhere. Like I mentioned, lots of low end Sun hardware used SCA. Nicest thing you can say is the drives were probably slightly better than the *really* doggy SCSI drives you’d find in a contemporary Macintosh.

The 2940UW is a capable controller and *should* be faster than the IDE port on that board, but as mentioned you need a really capable drive to max it out, and there’s also this huge amorphous stew of “SCSI Voodoo” that can really bite you. Issues with cabling, bad adapters, incorrect termination, a whole slew of things can cause your setup to fail to negotiate the highest possible speed. Using an SCA adapter at all makes me a little leery, I remember having all sorts of issues with those, again, cabling is vital…

Long and short of it is many, many people stubbornly refuse to shed any tears over parallel SCSI going away, for good reason.
 

twolazy

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I'll go ahead and get in line for one of the motherboards if you end up selling :)

Either way I have a spare motherboard and vrm., plus terminating slot bracket for external scsi connection, and corresponding cable. ;)

Purchased 2 machines last year , old 3com Superstack II rack servers. Pretty much new old stock. Have a month or 2 of use tops. They were used an hr or 2 a month to print labels. Got em in a trade and fee for a server migration.

As for SCSI 3, it kinda passed me by. I never got much experience with it. By time the hosptials upgraded by me, they moved to SATA/SAS from SCSI 2.
 
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