mdadm need help

[Mad Professor]

I'm playing with mdadm and I built a raid 5 array with 4x 500GB seagate drives for testing. I decided that I need to test onboard sata controllers.

I shutdown the machine and when I rebooted, I ran mdstat and nothing shows up.

I thought mdadm was automatic?

how I created the drives.

mdadm --create --verbose /dev/md0 --level=raid5 --chunk=64 --raid-devices=4 --spare-devices=0 /dev/sd{a,b,c,d}

what did I do wrong and how can I reassemble the array?

[meton_magis]

did
cat /proc/mdstat

show anything? Were there any error messages displayed anywhere?

are your device types in fdisk `fd` (linux raid autodetect) ??

[Mad Professor]

I said mdstat didn't show anything.

but I think I screw up.

I didn't partition the disks at all. because about the 10 guides/manuals didn't tell me I needed to even tho it was against my better judgement.

I just did the command in my last post, it put the devices together and formed md0

I was able to format the drive with ext3 and mount it to do my performance test. After that I decided that the pci raid controllers were not sufficient to meet my demands, I shut down the machine and unplugged the sata cables and plugged them into my motherboard and rebooted.

The drives come up but mdadm does not detect the raid 5.

Since my first post I decided to start over on the array and build a new one. I partition the drives with type fd with fdisk and then use mdadm to create the array.

[meton_magis]

ah sorry, I glared over the part about mdstat not showing anything.

I don't know if there is a right way / wrong way to do md devices, I was just going off of what I've done in the past. I've always partitioned the drives, using type fd, and they boot up OK.

[Mad Professor]

ah sorry, I glared over the part about mdstat not showing anything.

I don't know if there is a right way / wrong way to do md devices, I was just going off of what I've done in the past. I've always partitioned the drives, using type fd, and they boot up OK.

yeah it's all good. Thank you for helping me in my time of need.

Doing raid raw on disks doesn't allow automatic detection because the kernel doesn't detect the raw data superblock, you need a partition.

I redid the array with partitions FD on each disk and automatic detection works now, and now the array comes up in mdstat.

This is my second time playing with software raid. The first time I did raid 1 but it didn't mirror the second drive and when the first drive failed I had 100% data loss. I swore to myself I would never use linux raid ever again, bought some cheap rocketraid cards and now they are not working out on a new motherboard. PCI bus erratic and drops to 20MB/s using the highpoint drivers. but if I use the modules that comes with the kernel; I can get 50 MB/s W 70-90MB/s R but it's not sustained, very erratic and performance sucks. The PCI bus is 64Bit @ 66MHZ but still, compared to the onboard Nvidia sata which is able to sustain 100MB/s Write and Read with the same drives I tested, the performance is smooth. I tried a different PCI raid controller, a generic one I had, it was bit more stable on read, but write continue to be erratic. I tried single disk and raid 5 configurations and still got poor performance on the PCI but the onboard perform way better then PCI cards, which conclude that PCI is not optimized in coding of the bios and/or linux kernel, maybe not updated for my particular chipset.

So I'm ordering a new intel SASUC8I PCIe 8x card and do linux software raid 5 on 6 new 1TB samsung drives. Take the two 1.5TB and the 2TB samsung and use it for backups of the new raid 5 array via rsync. Repurpose the 500GB for other use like my myth box and another desktop computer.