Best place to put Parity Drive (PCI-X Board)


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I am new to Unraid, up until now I have used a Drobo 5D but decided to move to a system that I had more control over when a drive fails i.e. improve my chances of actually getting the data back.

 

To get me going I bought a secondhand system on ebay which has :

 

Supermicro H8DAE motherboard (2 x 2.4GHz dual core, 32GB ECC RAM, Onboard IDE only, 2 x 133MHz PCI-X 64bit slots, 2 x 66MHz 64bit PCI-X slots)

 

2 x Supermicro SAT2-MV8 PCI-X controller 133MHz PCI-X 64 bit, capable of handling 8 x Sata II each

 

15 SATA bay case

 

I also  have the following drives to go in :

 

1 x 6TB Hitachi 7200rpm Sata III

10 x 2TB Hitachi 7200rpm Sata III

5 x 4TB Seagate 5400 rpm Sata III (extracted from USB external drives)

2 x 250 GB Samsung EVO SSD drives

 

I have a couple of general questions that I would appreciate any thoughts on:

 

(1) I plan on using the 6TB drive as the Party drive, should I connect it to one of the SATA ports on either of the current SAT2-MV8 boards or should I install a third SAT2-MV8 specifically for the Parity drive. the issue I immediately see with adding a third SAT2-MV8 is that it will have to go on a 66MHz PCI-X slot because the two 133MHx slots are already in use but I am thinking that perhaps that is preferable to having the Parity drive share the PCI-X bus with the data drives.

 

(2) Should I alternate the 5400rpm and 7200 rpm drives across the two SAT2-MV8 cards or put all 5400RPM on one SAT2-MV8

 

(3) Is it worth fitting the SSD's as a cache pool i.e. with my board and cards am I likely to get the write benefit of SSD.

 

(4) I have more drives than connection points (16 SATA 2 connection points but 18 Drives). I have 30TB of data at the moment and it is growing about 100GB per day. Which drives should I abandon ? or should I go for the third (slower 66MHz) PCI-X SAT2-MV8 and add more drive bays ? or look at a second Unraid

 

(5) I have 3 x 8TB seagate archive drives. These are explicity banned from use on the Drobo so I'm using them as a second layer backup. Should I perhaps consider incorporating them into the Unraid system ?

 

I have read the FAQ and Manuals but its taking a while to absorb so I thought I would ask for some initial guidance to get me started

 

Many thanks in advance

 

Steve

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(1) I plan on using the 6TB drive as the Party drive, should I connect it to one of the SATA ports on either of the current SAT2-MV8 boards or should I install a third SAT2-MV8 specifically for the Parity drive. the issue I immediately see with adding a third SAT2-MV8 is that it will have to go on a 66MHz PCI-X slot because the two 133MHx slots are already in use but I am thinking that perhaps that is preferable to having the Parity drive share the PCI-X bus with the data drives.

 

I have no experience with this board but both pci-x 133Mhz slots share the same bus (and slots will be limited to 100Mhz when both are in use), so it may be faster (or the same) to use one 133MHz plus one 66Mhz slot.

 

In my view there’s no advantage of isolating the parity disk, it won’t make a difference in normal writes and for parity checks the total pci-x bandwidth will be the same.

 

If I’m understanding the board diagram correctly, your parity check will max out at about ~60MB/s when using 16 disks, this will improve considerably when over the 2TB position, since you’ll be left with 6 disks only.

 

 

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