Hello,
I have a HP ProLiant with RHEL6.
I would like to ask for advice to configure its 8 disks SmartArray cabin in an optimal way.
Currently the 8 disks are grouped in 4 RAID1 arrays. I would like to change to RAID 5 in order to increase the available storage space.
I'm doubting between 2 different options:
a) Keep the current RAID1 containing the Operating System, and build a RAID5 array with the other 6.
b) Build 2 RAID5 arrays with 4 disks each.
I don't know if there is a recomended maximum number of disks for building a RAID5 array. Perhaps 6 is too many?
Any comment will be wellcome.
Thank you.
Asun

In the past I've used a mirrored pair for the O/S and the rest of the disks in a RAID5 mounted accordingly. This was back when we had smaller faster disks for the O/S and slower larger capacity disks for storage.

These days for a GENERAL system I'd be tempted to go RAID6 with the lot and use LVM to provide partitioning. Obviously if your controller doesn't support RAID6 or you're not worried about mitigating against double disk failure then use RAID5.

You will however get a different opinion from just about everyone.

Oh, and there's no (practical) maximum number in a RAID5, in the past I've had HP DL servers with 16 disks, 2 in a RAID1 for the O/S and 12 in a RAID5 with 2 spares for the main data storage.

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Thank you very much, TenTenths.

I concur with TenTenths:

- RAID6 for the lot, as long as you don't mind the slight performance hit

- RAID5 otherwise

- LVM on top of RAID for ease of partitioning.

... obviously, if your system is UEFI, ESP requires special treatment, so plan accordingly.

Cheers.

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Personally I would go RAID10 - going through rebuild after a (double ?) disk failure might help explain why.

Disk is cheap - (people) time is expensive.

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The reason you are getting many differing opinions on an optimal RAID array is that there are many different things you can optimize.

Optimize storage capacity - RAID 5

Optimize protection against double disk failure - RAID 6

Optimize performance - RAID 10

You need to decide what you are optimizing.

With RAID 5/6 even if you have legacy BIOS your /boot partition requires special treatment. Linux can easily boot from a simple RAID 1 mirror but otherwise planning is needed. Either the /boot partition needs to be outside of the RAID 5/6 or the grub2 core.img second stage needs to have extra modules compiled (mdraid, lvm) into it. This second stage would also need to be stored outside of the RAID 5/6 such as in a 1 MiB BIOS Boot Partition for BIOS/GPT installations. A small part of each disk needs to be kept outside of the RAID array.

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That's only true for software RAID.

The OP has a ProLiant server with a SmartArray hardware RAID controller. The OS only sees the logical drives, and thus can boot from any kind of RAID set.

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Thank you all of you for your comments.
All are useful.
I need storage capacity, so I think I'll use (hardware, yes) RAID5 and take the (small, I hope) risk of having a double disk failure.
Of course, I have B-A-C-K-U-P.
Greetings