Question on RAID and ports.

[brandonb]

I bought a new 8 port SATA card for a file server. It has two SAS connections and with the SAS to SATA splitout cables you can get up to 8 SATA. I plan to connect 8 drives to the beast in a RAID 10 configuration.

The question being.

Are the resources shared between all 8 ports? So will it matter if I connect all the mirror drives to one cable, and the real data to the other cable (so the strip is on the same connection) or do I split it out evenly so the strip covers both cables? Or does it not matter?

This is the card I bought:

http://www.newegg.com/Product/Produc...-157-_-Product


So either:

Cable1     Cable2
Stripe      Mirror
Stripe      Mirror
Stripe      Mirror
Stripe      Mirror

Or

Cable1     Cable2
Stripe      Mirror
Mirror      Stripe
Stripe      Mirror
Mirror      Stripe

 

[imagoon]

SAS is a point to point model. I have not found the controllers channel count (hard to assume) It could already be 2 channels expanded to 8 or 8 channels.

Anyway is in RAID 1 / 10 it would be irrelevant since each drive is read anyway. PS you will be running SATA over SAS encapsulation so the SATA overhead might make the card slower than you expect.

 

[Emulex]

my p410 knows that its CAGE0 and CAGE1 so it puts drives in raid-10 across the two. i could lose cage0 or cage1 and continue to rock out. you can tell by failing the drives or watching the lights carefully. p410 has two sas cables to two drive cages

 

[brandonb]

SAS is a point to point model. I have not found the controllers channel count (hard to assume) It could already be 2 channels expanded to 8 or 8 channels.

Anyway is in RAID 1 / 10 it would be irrelevant since each drive is read anyway. PS you will be running SATA over SAS encapsulation so the SATA overhead might make the card slower than you expect.

I've setup the raid. Apparently the raid card is RAID 1E, which doesn't have quite the mirroring/striping ability (performance wise) as RAID 10, or so certain forums say. I do have it setup, but I am only sustaining about 30-35MB/s... Do you know how slow the encapsulation may make it? It seem slower than I was expecting, but I can live with it, I suppose.

The only thing I'm really hoping to achieve is to be able to playback blurays on the machine. But according to the Blu-ray Disc specification, 1x speed is defined as 36Mbps.

I should be fine even at 30-35MB/s. No biggy.

 

[imagoon]

Overhead varies from card to card. There is the protocol over head plus the processor time. I have seen as much as 20% however depending on how well the controller handles "sata."

 

[greenhawk]

It proberly does not matter enough to worry average usage. The bottle neck is either from the card to the rest of the system or is part of the controller. The cable to the drives ranks rather low in the performance numbers after these two. Besides which, if a cable did mater, you would only see a difference if you could be assured the data you want is on that drive. Running a raid 1 means having a fast connection is lost when the second mirror drive is on a "slow" connection.

Not something to make your choice on personally.

As to how to do it, I would ensure the mirror of a drive is not on the same cable incase the cable comes loose. Beyond that, any way that works for you. (have all the mirrors on the same cable can also mean you can use separate power cables to separate the drive arrays onto different power rails if your power supply has that feature (ie: drive freezes/shorts the power to it, the mirror or main ones go down, not parts of both)).