1 TB disk

is finally here. Tech Report has tested the new Hitachi 7K1000 hard drive. Some quick facts are:

  • 32 MB cache
  • 200GB per platter that gives a data transfer rate of 300MB/sec
  • UER of 1.0E15 bits or 1.0E14 bytes transferred, which means that we will encounter an error after a disk is read for about 100 times.

There may be many techniques for getting around with the UER problem. For example, we may, for scrubbing, use only oppurtunistic scanning so that we don’t end up scanning the surface separately.

Jim Gray (now missing, lost into the seas) predicted that the pipe that comes out of the hard disk is not getting fat, while the storage tank itself is getting fatter. With the recording density increasing, one can see that the throughput is also increasing. 300MB/sec is app. 10 times better than that of a normal disk, which means that an entire disk can be read in about a couple of hours!!

What are the new problems that may arise with a 1 TB disk? With the data capacity increasing, any complete disk scan operation (like disk scrubbing, backup, indexing etc.) will increase the chances of facing an unrecoverable error. So, these disk sweep operations have to be kept at minimum or have to be batched.

Another problem is that failure of a disk results in the loss of an entire TB of data. No point in going for a RAID-5 drive, if you cannot afford more than two disks. Even if you, Robbin Harris has already pointed out that RAID-5 won’t work as the number of disks in the RAID-5 array increases. So, it mostly have to be a mirrored data.

Geeki’s take:

I have learned that there are two kinds of people in this world: those who crib/complain and those who do not.

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