I'm getting 2 1.5TB drives this week (Dell $100 ones) and a cheap 4 port PCI SATA card. I have 6 MB ports, 4 PCI-e ports and 4 PCI ports. To start I must move 1 HD to the a PCI port (and more soon). I'm waiting/hoping for the Supermicro AOC-SASLP-MV8 - 8 Sata PCI-E card to be made compatible (please, please hurry Tom). My first thought was to move the parity drive to the PCI slot since it is only used for parity checks and copying (done at night).  However the FAQ says it needs to be on the fastest (MB) port.  Why is this since it's idle most of the time (and about all the time that speed is important)?  How about my cache drive? I know it's a 1.5Mbps SATA drive but I do copy a lot to it , so it's used a lot.  All my drives are used as shared shares (with HD (Blu-ray) video), except #7 which is a detected music share which runs 24/7.  What would be the first drive to move to the PCI bus and then what would be the second?

 

I would not go with the cheapest PCI card. (Although this depends on your motherboard).

The Promise TX4 has a FIFO buffer, is known to be compatible and can support a 66Mhzx PCI Bus if your motherboard supports it.

 

That being said, I would put as little as possible on the PCI Bus.

 

If had to move parity onto the PCI bus then that would be the only drive I would put there. (or the cache drive).

 

During any write operation it will have to be read and written to.

The speed of the PCI bus is a maximum of 133MB/s. (266/mb if 66mhz bus).

A PCI-e 1X port is about 250MB/s.

Drives these days range from 60-120MB/s.

 

>>> How about my cache drive? I know it's a 1.5Mbps SATA drive but I do copy a lot to it , so it's used a lot.

I would probably move my cache drive there and that would be the only drive on that bus (if possible).

Since the drive seems to be a SATA I drive and the bus speed maxes at 133MB/s then you will not be loosing much.

The Gigabit ethernet is the real bottle neck to your drive so you will probably be fine.

When moving data from the cache to the array it will be moving mostly in one direction so you'll be fine there.

 

 

>> However the FAQ says it (PARITY) needs to be on the fastest (MB) port. 

>> Why is this since it's idle most of the time (and about all the time that speed is important)?

 

If you are using a cache drive, then you can get away with parity being on a slower bus if you do not mind the extra time involved later on.

When parity is updated (write to  data drive), parity is read, data drive is read, Current data is xor-ed out, New data is xor-ed in, Parity drive is written, data drive is written.

It's the read & write of every updated sector that slows down updates to parity protected drives.

if you use a cache drive, this is done overnight.

If you re-calculate (or check) parity then any drives shared on that bus, must share the bandwidth of the bus it is on.

 

 

What motherboard are you using?

I have a Supermicro C2SEE MB. the reason I'm going with a "cheap" PCI card is it's temporary until the Supermicro's SASLP-MV8 8 port PCI-E is supported or I have to by another 4 port PCI-E card. So for my situation it looks like a toss up for either the cache or the parity drive to go on the PCI bus. I may go with the parity since it will likely offer the least performance reductions.

 

Lets say I put the parity now and I buy another drive before the Supermicro's SASLP-MV8 8 port PCI-E card. Would/could I put both the parity and the cache on the PCI card (keeping all data disks on MB/PCI-E)or would this be a problem?

 

 

I have a Supermicro C2SEE MB. the reason I'm going with a "cheap" PCI card is it's temporary until the Supermicro's SASLP-MV8 8 port PCI-E is supported or I have to by another 4 port PCI-E card.

 

http://www.supermicro.com/products/motherboard/Core2Duo/G45/C2SEE.cfm

If I have found the correct board, it supports PCIe 1X.

You can get a 2 port PCIe 1X card for $20-$30 range.

You could move parity and cache there safely and keep both operating at highest speed.

Especially since you will be using one or the other, but probably not writing to both at the same time.

 

PCIe is full duplex bus which means you can be going in one direction at 250MB/s and the other at 250MB/s at the same time.

 

 

Lets say I put the parity now and I buy another drive before the Supermicro's SASLP-MV8 8 port PCI-E card. Would/could I put both the parity and the cache on the PCI card (keeping all data disks on MB/PCI-E)or would this be a problem?

 

I'm sure you could get away with it. You most likely would not be writing to both at the same time except for the mover overnight.

However you will be reading from one (cache), then reading from the parity, reading from the data drive (on the higher speed bus), re-writing to the data drive, then re-writing the parity block.  I don't know the order of the system calls, but you might get away with it.

 

As I mentioned in the other post, I would probably put the cache drive on the PCI bus considering it is only SATA I (150).