Member Avatar for merly

Hello,

I would be grateful for information regarding RAID and Ubuntu about hardware.

I want to build a computer that will be a Ubuntu computer with hot swap RAID 1 using SATA 2 (3Gb/s) hard disk drives.

1. Can I just get two SATA hard disk drives, install them in a caddy (for example a SATA 2 version of http://myahead.com/go/look/product.show_product?v_id=4734) and the connect the SATA cables directly from the caddies to the hard disk drive controller on the motherboard, leave the motherboard's software RAID functionality switched off, and then install Ubuntu using Linux's Multiple Device (md) feature which is installed with Ubuntu to create a software RAID system? I don't know if the end result would be hot swappable? The Ubuntu Wiki page on RAID (https://wiki.ubuntu.com/Raid) recommends using md which is why I'm asking how to go about this. Or is the only way to get hot swap RAID, by using a real hardware RAID controller (e.g. 3Ware) to connect to the two disk drive caddies?

2. Does it matter whether using PATA hard disk drives or SATA hard disk drives?

Regards,


Merly

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Short answer: software RAID (md/mdadm) will do the job; whether drives are hot‑swappable depends on the SATA controller/backplane and firmware, not mdadm. On motherboards that expose native SATA/AHCI (or a proper HBA) the kernel will see remove/insert events and an md RAID1 array can be rebuilt online. A hardware RAID card (3Ware or similar) will also provide hot‑swap support and drive LEDs/management, but it isn’t strictly required.

Practical setup notes and gotchas: keep partition layouts identical (same sizes and types) on both disks so replacing a drive is painless. Make /boot available to the firmware by either placing /boot on a small RAID1 partition or installing the bootloader to both disks’ boot records so the machine can boot if one disk dies. Save mdadm config (mdadm.conf) and rebuild initramfs after array creation so arrays assemble at boot.

Common maintenance sequence (example) for replacing a failed mirror member — mark it failed, remove it, swap the drive, then add the new device back to the array:

sudo mdadm --manage /dev/md0 --fail /dev/sdb1
sudo mdadm --manage /dev/md0 --remove /dev/sdb1
# replace physical drive in caddy/backplane
sudo mdadm --add /dev/md0 /dev/sdb1

Monitor kernel and udev events with dmesg or udevadm monitor to confirm the hotplug is seen. If insert/removal events are not appearing, the controller is likely running in legacy/IDE mode or the backplane isn’t wiring the hot‑plug pin—switching to AHCI/native mode or using a proper hot‑swap backplane/HBA resolves that.

PATA generally lacks reliable hot‑plug support; SATA (and SAS/SCSI controllers) are the right choice for hot‑swap. As noted, software RAID works well; ’s SCSI example illustrates that the controller/backplane is what makes hot‑swap seamless.

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Member Avatar for DimaYasny

should work. not sure about the HOTswap, but the usual raid1 functionality and redundancy are present. btw linux software raid is very easy to manage through webmin

Member Avatar for jbennet

i have a compaq proliant 1600r and its hotswap SCSI raid drivers work with linux

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