raid 0 parity on motherboard sata

[gidderman]

Hello all, so i am posing a 2 part question or 2 different questions that are related here depending on how you look at it.

I am going to set-up an unraid server for multiple uses as most of you here have, and i am going to use 5 disks and 1 ssd off the hop

The setup i am aiming for is as follows:

5 disks, 4-4tb and 1-8tb  --- configured 2-4tb in raid 0 on the motherboard for parity, and the other 3 disks as file storage on the hba

1 ssd -250gb 850evo as cache on the motherboard sata port

motherboard is asus prime z370-a

hba is lsi sas9211-8i flashed to it mode 20.00.07.00 - with bios for now

 

So, my question(s) are:  1. can i mix usage of the motherboard ports and hba ports for this array, or will there be conflicts. Has anyone done this before?

2. Can i configure the raid 0 parity drive on the motherboard hardware, or should i be using the unraid software to do the raid 0 config of the parity? Also, can i use another motherboard sata port for the cache drive and put my data disks on the 9211-8i (related to question 1)

 

I have tried to find some info on this abroad but not as of yet been able to find any clear answers.

 

I am intending on using every sata port available in the system at some point as i expand my array, but are there any known issues with mixing motherboard sata controllers and hba controllers for a single array? Any performance losses, conflicts, etc? Has anyone done this or similar config?

 

Thankyou All for your Help!

Edited March 22, 2020 by gidderman

[Squid]

23 minutes ago, gidderman said:

1. can i mix usage of the motherboard ports and hba ports for this array, or will there be conflicts. Has anyone done this before?

Yes. No problems.  I run 4 drives (+ nvme) off my motherboard, along with a pair of HBAs each running (one runs 8 drives, the other 12)

 

23 minutes ago, gidderman said:

Can i configure the raid 0 parity drive on the motherboard hardware

The "RAID" on the vast majority of motherboards (especially consumer boards) is not RAID regardless of what it implies.  Rather, it simply signals to Windows to set up those ports as a software raid.  So, no it will not work

 

25 minutes ago, gidderman said:

should i be using the unraid software to do the raid 0 config of the parity?

Even if you could do a RAID0 on parity, it really doesn't get you anywhere as you would still only be able to handle a single data disk failure.  What you want to do is have unRaid set up 2 drives as a dual parity (they are not duplicates of each other) so that you can handle dual drive failures simultaneously

 

[trurl]

I think your approach will just be more trouble than it's worth. Unraid does not do RAID itself, except for various btrfs raid configurations in the cache pool.

 

Best to not use any RAID controllers, and just use the 8TB drive as parity and the others for data. With that 8TB as parity, you will be able to replace any of your other disks with larger disks later (up to 8TB).

 

Even if you could do 2x4TB RAID0 as parity, it is not certain whether or not that 8TB would be large enough to allow a standard 8TB data drive in the array.

[Squid]

Yeah, didn't read the OP fully enough to realize he was trying for 2 x 4TB to handle the parity for an 8TB disk.  But now realizing that,  if you could do that then you have exactly doubled the chances for the parity to fail.  

[gidderman]

Hello all. Thankyou for your replies.

 

To be clear here i am going for multiple write performance over reliability here. I understand that the parity drive in raid zero could fail, but it is not double the chance of failing, it is the same as if there was one disk, and it failed. If one of the parity drives fails in raid 0, i will simply pull the drives, replace them both and get a 4tb spare to keep from it.

 

I cant seem to find any clear answers anywhere about this particular use case, so i will just attempt it and post the results. Now that my kingston 16gb se9 has arrived, let the trials begin....

[itimpi]

I did trial using 2 x 4TB as an alternative to a 8TB parity drive.     What I found was that the 2 x 4TB ended up having slightly less space than a genuine 8TB drive so it still did not let me use 8TB data drives.

[JorgeB]

You can get better speeds if all array devices are in RAID0, just having parity it's not really worth it IMHO, also like mentioned SATA fakeRAID won't work for that.

 

I have a small server where each array device (including parity) is a RAID0 of 2 disks on an LSI 9240, you can also use any LSI 9211 or similar flashed to raid mode, but note that those are limited to two raids groups max, only megaRAID controllers like the 9240 or above support more.

[trurl]

10 hours ago, gidderman said:

To be clear here i am going for multiple write performance over reliability here.

Unless you set things up so the multiple writes occur on different data disks, it won't matter at all since the data disk being written will be the deciding factor no matter how fast parity is.