Re: 12-15 TB RAID storage recommendations

["nate" <centos@xxxxxxxxxxxxxxxx>]

John R Pierce wrote:

> well, IF your controller totally screams and can rebuild the drives at
> wire speeds with full overlap, you'll be reading 7 * 2TB of data at
> around 100MB/sec average and writing the XOR of that to the 8th drive in
> a 8 spindle raid5 (14tb total).   just reading one drive at wirespeed is
> 2000,000MB / 100MB == 20,000 seconds, or about 5.5 hours, so thats about
> the shortest it possibly could be done.

More likely your looking at 24+ hours, because really no disk system
is going to read your SATA disks at 100MB/second. If your really lucky
perhaps you can get 10MB/second.

With the fastest RAID controllers in the industry my own storage
array(which does heavy amounts of random I/O) averages about
2.2MB/second for a SATA disk, with peaks at around 4MB/second.

Our previous storage array averaged about 4-6 hours to rebuild
a RAID 5 12+1 array with 146GB 10k RPM disks, on an array that was
in excess of 90% idle. Rebuilding a 400GB SATA-I array often
took upwards of 48 hours.

nate


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