Maxtor Atlas IV 80 pin to 68 pin

[rhturner]

It seems that the supply of Maxtor Atlas IV with the 80 pin SCA-2 connectors is big, while the supply of the 68 pin native drives is very low.

With that said, I purchased 1 80 pin Atlas IV in preparation to put 3 of these things on a RAID 0 stripe for a new machine I am building. Of course, all the adapters out there are 68 pin.

So, is there anything lost by going to 68 pin as opposed to 80 pin? Seems the SCA-2 controllers are reserved for server drive rackmounts. And has anyone already done this, and can recommend the best controller (Ultra 320) and the pin adapters (80 to 68) for these drives?

I really appreciate the responses.

Thanks!
Ryan

 

[Crashman]

Hehehehehehe.

68 and 80 are on the same transfer standard. 80 has extra pins for power and drive ID, plus the regular 68 pins, all in one package.

The purpose of 80-pin drives is for making them hot-swapable. Most hot-swap SCSI drive racks use 80-pin drives and have a 68-pin connector for the cable that goes to the PC.

You see so many 80-pin drives because they come out of these huge drive racks, large companies usually have several banks of them, dozens or hundreds of drives! That easily outnumbers the number of drives you see in workstations. And these drives are replaced more often, while workstations usually keep their drives to the death.

So what you need is a 80-pin to 68-pin adapter. Most drive wholesalers/refurbishers sell these things.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[rhturner]

Thanks. From my own research, it appears not all adapters are created equal, and many are not rated for U320 (just 160). I contacted the company that first created adapters, and appears to be making the best adapters which support 320. They are located at cselex.com. Awesome people to talk to.

A couple other questions....
1) It holds true in IDE world that hardware RAID 0 is slower than software RAID 0. It turns out that the proc's on the hardware raid cards can't be of benefit when compared to the super speed procs on the mainboard (for software raid 0) because raid 0 only requires a few cpu cycles. Is this true for SCSI? I would assume so... I ask because I dont need any other RAID support than 0. I would have to pay a small fortune to get an adaptec Raid card, while I could save a lot using HostRaid on a SCSI controller.

2) It appears Write-back cacheing is disabled by default on most SCSI drives. The Western Digital Raptor looks really good on tests when compared to SCSI drives, but it has write-back enabled by default. Is there great benefit for speed in enabling write-back on the SCSI drives?

Again, I need no data protection. This is a personal desktop, and anything important will be backed up.

 

[lunitic]

1. I'm really surprised about this. It would be the first time some specialized hardware is slower than a generic processor. Like, my graphics card is slower than my CPU. Like, a hardware MPEG2 (de)coder is slower than a software codec. I would have thought overhead and latency with a generic CPU far outweights clockspeeds.
Well, another dent in my ego. Could you give me any sites where this is discussed?

Anyway, as I would have expected hardware Raid 0 (on IDE) to be faster than software Raid 0, I would expect SCSI raid 0 to be even faster, especially because SCSI controllers tend to be more expensive and versatile.

2. IDE drives benefit from the fact that IDE doesn't support overlapped IOs, i.e. a write command has to be completed before another one can be issued. So the controller must wait while the data is physically written to the drive. Then the controller can transfer new data, then the drive can write, etc, etc. (In ancient times you could low-level-format a disk with several sector numbering sysems to avoid that the next sector was passed before the data transfer was completed, otherwise you would have to wait for the disk to turn another cycle. You needed to choose the best numbering system in comparison with the system speed). The write back cache makes it possible to start another data transfer immediately. SCSI supports overlapped IO, therefore enabling the write-back cache performance gains are considerably less.

 

[Crashman]

First of all, u320 doesn't matter. Drives can't transfer faster than the old u80 standard! It WOULD matter if you had several drives on the same cable, having all of these u320 drives which are actually slower than 80MB/s on one cable could push the total transfer to u320, but that would require MANY drives. So if the u160 adapters are cheaper, I'd go with those.

1) Depends on the power of the processor on the card.
2) Not sure

If you want a cheap RAID 0 or RAID 5, I have a 3 channel server card here I can sell you.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[rhturner]

lunatic,
here is the link with some pretty good benchmarks of software raid versus hardware raid. there is an entire section on raid 0 configs. This report is very long, but I think you will see hardware offers next to nothing if all you are doing is running raid 0...

http://www.anandtech.com/storage/showdoc.html?i=1491&p=1

I think I am going to stick to all 320 hardware. I have 3 drives now, but may go to 5, and I would just prefer to spend a little more money and make sure everything has the potential to perform as well as possible.

 

[Crashman]

Do you have a 64-bit PCI bus? How many drives do you plan on using?

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[rhturner]

The motherboard I will be purchasing will have a PCI-X slot. I will also be waiting for the new AMD 64bit procs and boards due out soon. At a bare minimum, I will have 3 drives (already ordered). I am already thinking of pushing that to 5. depends on how much space I feel I need, although chaining 5 drives on RAID 0 is really pushing my luck as far as losing all my data for 1 drive failure.

What adapter are you looking to get rid of?<P ID="edit"><FONT SIZE=-1><EM>Edited by rhturner on 09/19/03 09:05 PM.</EM></FONT></P>

 

[Crashman]

OMG, 3 drives in RAID 0? How do you plan on that, using a 3 channel card with 1 drive per channel? 5?

You know when it comes to Level 0, EVEN numbers of drives make more sense! Like, 2 drives across 2 channels, 4 drives across 2 channels, 6 drives across 2 or 3 channels, etc.

Of course RAID 1 would REQUIRE even numbers of drives, but RAID 0 just seems more logical with even numbers. 3 drives on 2 channels would be 1 drive on 1 channel and 2 drives on the second. Seems like the 1 drive would respond faster than the other two.

3 drives makes more sense in RAID 3 or 5.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>

 

[rhturner]

I must be missing something or not understanding something. I dont think I said I was using more than 1 channel. I plan on having 1 channel which has 3-5 disks on RAID 0. I don't see why having an odd number of drives would make a difference for RAID 0. In fact, seems like a lot of people have 3 (from my reading). Maybe you can enlighten me why this would adversely affect performance.

In fact, several reviews of RAID 0 sets were using 3 drives in the set. Doesnt make sense to me that this would be a bad configuration as multiple well respected sites are using that setup...

<P ID="edit"><FONT SIZE=-1><EM>Edited by rhturner on 09/20/03 00:02 AM.</EM></FONT></P>

 

[Crashman]

Having them all on one channel would hurt performance because the controller can't read from or write to all the drives at once, as far as I know.

<font color=blue>Only a place as big as the internet could be home to a hero as big as Crashman!</font color=blue>
<font color=red>Only a place as big as the internet could be home to an ego as large as Crashman's!</font color=red>