Some RAID questions, hw vs sw, suitable RAID card or HBA for OMV

SaleB · 20. September 2014

I have posted the wrong question in a wrong thread, but I have put that in order now. As I have mentioned in New OMV user, new build, I intend to make a RAID 1 of 10-14 drives.

About RAID. I have no experience with RAID. About hardware RAID people say it is not good for home users because of the complications that come after a controller hardware failure. I was not able to find what happens it a hardware raid card fails and is replace with the same one. e.g.: I have found a PCIe card on eBay "3ware 9590SE-16ML" which is a hardware SATA II card, it is used and it is cheap in my opinion (130eur) for a 16 port card. I have also found many other same generation 3ware cards and some Areca card that have it's own processor and RAID microcode which should make them real hardware RAID cards (cards that were new a few thousands euros). If I buy two identical cards and have one in a computer and another in a spare parts drawer, will I be immune to a problem of RAID card dying on me?

What is more advisable to use in my case (I do not know how much dose the number of drives impact the performance of software RAID) a hardware RAID card or OMV software RAID (I presume mdadm)? If I use software RAID, what type of car should I use a simple HBA, port multiplier based card, a real hardware based RAID card (like the one above) in JBOD mode or something else?

One more question, is there somewhere a list of cards that are supported by the OMV or known good candidates?
I have tried to find out which card supports Debian 7, but as most of these cards were made before Debian 7 I did not have any luck finding what I was looking for.

As I have on my motherboard one pcie 16x and two pcie 1x slots and 6 onboard SATA's, if I use software RAID, 8 port card is enough (maybe LSI 1068e), but if I use hardware RAID I do need a 16 SATA port card, because I have a socket for only one card (I have seen that many of these cards are pcie 4x or pcie 8x, but rare one's are pcie 1x and they have only two SATA ports).

In short:
1. hardware or software raid?
2. Which 8 port controller card?
3. Which 16 port controller card?

Thankful in advance,
SaleB

davidh2k · 21. September 2014

Zitat von SaleB

them real hardware RAID cards

Yes, the LSI/3ware cards are real hardware RAID. Can't say something about the other ones.

Zitat von SaleB

will I be immune to a problem of RAID card dying on me?

Immune? No. But you're decently prepared. But you should consider a PSU or the BBU for the HWraidcontroller if you want to go down that road.

Zitat von SaleB

(cards that were new a few thousands euros

Well, not that expensive, but the 16-Port 3ware was around 800 € Retail if I remember correctly.

Zitat von SaleB

(I do not know how much dose the number of drives impact the performance of software RAID

I would say barely any impact on the number of drives. I even doubt that RAID1 needs much CPU processing.

Zitat von SaleB

I presume mdadm

You presumed right.

Zitat von SaleB

If I use software RAID, what type of car should I use a simple HBA, port multiplier based card, a real hardware based RAID card (like the one above) in JBOD mode or something else?

Any standard SATA Controller will do. For software raid stay away from the expensive ones, they are just a waste of money in that case.

Zitat von SaleB

One more question, is there somewhere a list of cards that are supported by the OMV or known good candidates?

Well, only thing you need to know is if the card works on Debian. Nothing else.

Zitat von SaleB

In short:
1. hardware or software raid?

You will be fine with just software RAID.

Zitat von SaleB

2. Which 8 port controller card?

Zitat von SaleB

3. Which 16 port controller card?

Any Sata Controller card will do for software RAID.

Zitat von SaleB

I have been thinking about redundancy and RAID 5/6 does not do it for me.

Zitat von SaleB

I lose only the data from that drive and I want to keep that commodity so RAID 1 (or perhaps RAID 10) is the only option that I can consider.

Zitat von SaleB

I intend to make a RAID 1 of 10-14 drives.

You do know that making 10-14 drives with RAID 1 is a biiiiiiiiiiiiiig waste of drives, which makes me ask why you ruled out RAID5/6 so quickly.

Oh, and btw: In you scenario, I would not even use RAID1. I would consider an rsync solution allways better than the RAID1. RAID1 does not protect you from accidential deletion, where an rsync backup would protect you.

Greetings
David

PS: I personally use Hardware RAID.

SaleB · 26. September 2014

Thanks for the answers, you helped me.

Yes, I am thinking about RAID5, but as I am not in a situation to buy drives in large quantities at one time, I intend to make RAID1's whenever I buy a drive. When there is 10-14 drives, I can use half of them as RAID5 and the rest as backup, but for now I must go a drive at a time, so RAID1 is the only option. Just one question here, a drive that is removed form a RAID1 array, can it be used as a single drive with the data on it still readable?

I have talked with LSI support in recent days, they are not certain that B85 chipset would be compatible with their cards. So that leaves me to Areca, Highpoint or something else, anything that supports JBOD. I will go with the software option.

Thank you

davidh2k · 26. September 2014

Zitat von SaleB

Just one question here, a drive that is removed form a RAID1 array, can it be used as a single drive with the data on it still readable?

To be sure buy one more drive in the end and revert your raid 1s to single disks one after another and then form your raid5.

Greetings
David

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