Long RAID 5 expansion time?

I'm currently expanding my Dell PERC 5i RAID 5 array from six 1.5TB drives to seven 1.5TB drives, and so far it has taken 28 days to get to 95% completed. The array was about 96% full when I started the expansion. Do these RAID 5 expansions usually take this long, or am I just overwhelming the poor PERC 5i with too many full disks?

That sounds a bit slow, but remember that is older hardware. Is the drive mounted or do you have anything using it? What "rate" do you have it set to in the configuration? For example, if I set my RAID card to "10" (out of 100) for the rebuild/expand rate, it is going to rebuild very slowly, but the array will still be usable.

I expanded an array from eight (8) 2tb drives to nine in around 45 hours with a rate of 85 on a LSI 8708-EM2.

I am not sure what 'rate' I'm asking it to rebuild at. However, transfer speeds off the networked server is about 2 MB/s vs the 90+ regular, so I would imagine it would be considered a higher rate.

I am not actively using it, but it can still be seen in Windows and over the network, so I can still grab files off it or do quick backups when I need to.

neonblingbling said:

I am not sure what 'rate' I'm asking it to rebuild at. However, transfer speeds off the networked server is about 2 MB/s vs the 90+ regular, so I would imagine it would be considered a higher rate.

I am not actively using it, but it can still be seen in Windows and over the network, so I can still grab files off it or do quick backups when I need to.

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The drives have to seek from the cylinders they're currently copying for the expansion process to your user data. Depending on the block size your OS uses that can mean a significant reduction in data rate, easily by a factor of 10 to 100. It's basically the difference between sequential data rate and random.