SAS data cable

Khannie

Sooo....In the quest of superior performance I have an SAS drive and perc 5i controller card on the way. The controller card has an sff-8484 interface. What I'm wondering is this:

Will the sata power connectors from my PSU power the drive?

If so, is this the cable I'm looking for for data transfer? (I'd like the option of connecting sata drives to it at some point).

Khannie

Surely to jebus some of you have SAS experience?

Stephen

The only experience I've had with SAS drives is with HP servers where they just plug into the front of the server without any cabling

Are these the older, physically larger SAS drives or the newer laptop sized ones?

Khannie

Stephen wrote: »

The only experience I've had with SAS drives is with HP servers where they just plug into the front of the server without any cabling

A lof of the HP / Dell ones seem to come in cages like that for hot swapping etc.

Stephen wrote: »

Are these the older, physically larger SAS drives or the newer laptop sized ones?

I haven't seen it yet actually. It's in the post as we speak. The dimensions are:

"Disk Size: 5.75"x4.0"x1.0" (Low Profile Hard Drive)". I'm thinking that's the old style.

Khannie

Hmmmm. I just found a nice close up picture online.



Looks like it's the standard 7 pin connector for data alright. Also 15 pins for power looks the same. Seems like the cable is correct then. €42 euro including shipping for the cable = ouchies.

10-10-20

That's what's called an SCA connector- a generic name for a data and power connector for use on a backplane. It's designed for hot(warm)-swapping and such.
What you will have to do is separate the power and data components from this connector block, possibly through the use of a suitable SCA converter.

Just on another point - where are you getting the disk drive from? From the same source as the PERC controller?

Also, do you already know what the various cache settings are for the controller?

10-10-20

Stephen wrote: »

Are these the older, physically larger SAS drives or the newer laptop sized ones?

That's 3.5 inch versus 2.5 inch.
The PERC5i will work with SAS as well as SATA by-the-way.

Khannie

10-10-20 wrote: »

What you will have to do is separate the power and data components from this connector block, possibly through the use of a suitable SCA converter.

You lost me at hello.

For the data part I was gonna use the cable I linked in the first post. For power I was gonna use the SATA connectors from my PSU. Am I right in thinking that's ok?

10-10-20 wrote: »

Just on another point - where are you getting the disk drive from? From the same source as the PERC controller?

Ebay tbh. I got the perc controller and drive from different people.

10-10-20 wrote: »

Also, do you already know what the various cache settings are for the controller?

Eh, maybe. The controller comes with 256M of cache ram. I intend using that for read caching at least. A mate of mine in dell tells me that the controller disables the on-disk cache, but with the 256M I don't think that'll be a huge issue.

I installed a controller manager program from Dell to have a look at it (before the card arrived). I think that has everything I need to make it go like the clappers.

10-10-20 wrote: »

The PERC5i will work with SAS as well as SATA by-the-way.

I had found that out alright from googling around a bit.

10-10-20

First off... for reference:
http://support.dell.com/support/edocs/storage/RAID/PERC5/en/index.htm

Khannie wrote: »

You lost me at hello.

For the data part I was gonna use the cable I linked in the first post. For power I was gonna use the SATA connectors from my PSU. Am I right in thinking that's ok?

OK, the connection on the hard drive is called an SCA. This simply a combined power and data connector. You need a converter to move from the combined format to the standard SAS format... For example:
http://www.cs-electronics.com/sas-products.htm

Ebay tbh. I got the perc controller and drive from different people.

Eh, maybe. The controller comes with 256M of cache ram. I intend using that for read caching at least. A mate of mine in dell tells me that the controller disables the on-disk cache, but with the 256M I don't think that'll be a huge issue.

OK, that's something that you are already aware of. Most OEM drives destined for use in servers / storage have the onboard disk cache disabled to prevent data loss in the event of a power loss. The PERC has a battery backup which preserves the data on the 256MB cache in this event.
Depending on the environment, it's not critical to have, but is wise.

For performance, you need to set the write cache to - WRITE BACK, the read cache to ADAPTIVE.
Ref: http://support.dell.com/support/edocs/storage/RAID/PERC5/en/UG/HTML/chapterh.htm#wp1069357
Play around with these settings to find out what suits you. You can modify these on the fly without any affect on your data, but you cannot change the stripe-size without deleting the config.

From the management utill you can change (reconfigure) the RAID setup (ie. from RAID-1 to RAID-5 and back) on the fly, but this is highly intensive.

I installed a controller manager program from Dell to have a look at it (before the card arrived). I think that has everything I need to make it go like the clappers.

Out of interest, what application did you use? You may be forced to simply use the CTRL-R at boot-time as the management applications can be locked down to specific systems.

Khannie

Thanks for the reply. Very helpful. Much appreciated.

10-10-20 wrote: »

OK, the connection on the hard drive is called an SCA. This simply a combined power and data connector. You need a converter to move from the combined format to the standard SAS format... For example:
http://www.cs-electronics.com/sas-products.htm

Ok, I'm looking at this cable or this cable for the win. Is that right? It looks like it should fit.

After more googling, I found this image on toms, which shows why the cable in my original post wont work (top is sata, bottom is sas).

For performance, you need to set the write cache to - WRITE BACK, the read cache to ADAPTIVE.

Nice one. Thanks.

Out of interest, what application did you use? You may be forced to simply use the CTRL-R at boot-time as the management applications can be locked down to specific systems.

I'm running gentoo linux on the box I'll be installing the drive. I downloaded a file called SSM_linux_installer-2.16-01_ESG.tar.gz. There are a few RPM's in this and gentoo supports RPMs, so I installed it, and fired it up. Seemed to work ok, but told me there were no controllers (correct for now).

edit: Jeez. Just reading a bit of the dell documentation there. There really is a lot to it compared to just sticking in an SATA controller and adding a drive to it. My configuration will be jbod. Single disk for the OS which I will partition myself and back up regularly to my software raid 5 array. Hopefully this will simplify things.

Khannie

I ended up buying one of these for semi-reasonable money on ebay ($36 including shipping). The next cheapest I could find was a four drop for $75 including delivery.

10-10-20

I wasn't aware of that cable, but yes, that will do the job!

Khannie

Grand job. Cheers.

On the minus side, it seems the perc 5i isn't compatible with my motherboard (Asus P5W DH Deluxe). :mad: I paid really good money for that board.

I updated the bios this morning. Will check the card when it arrives then set about changing the motherboard if that turns out to be the case. Pain in my lady flower.