WD's Monster 2TB Caviar Green Drive, Preview Test

MojoKid writes "Today Western Digital is announcing their WD20WEADS drive, otherwise known as the WD Caviar Green 2.0TB. With 32MB of onboard cache and special power management algorithms that balance spindle speed and transfer rates, the WD Caviar Green 2TB not only breaks the 2 terabyte barrier but also offers an extremely low-power profile in its standard 3.5" SATA footprint. Early testing shows it keeps pace with similar capacity drives from Seagate and Samsung."

Comments

Re:32MB On Disk Cache

[drsmithy]

If the HDD does the same caching according to nearly the same principles, won't the data on the disk cache nearly always be a subset of the disk cached in RAM? Meaning: doesn't the disk cache have no effect whatsoever?

No, because the OS does not know about the physical layout of sectors on the disk and the HDD controller does. Therefore, it can reorder requests appropriately to maximise performance.

Disabling the cache on a hard disk gives a massive performance hit, especially for writes. They become nearly an order of magnitude slower.

Re:backups

[bendodge]

There's another problem. Take a look at this excellent article:
http://blogs.zdnet.com/storage/?p=162

SATA drives are commonly specified with an unrecoverable read error rate (URE) of 10^14. Which means that once every 100,000,000,000,000 bits, the disk will very politely tell you that, so sorry, but I really, truly can't read that sector back to you.

...

Disk drive capacities double every 18-24 months. We have 1 TB drives now, and in 2009 we'll have 2 TB drives.

With a 7 drive RAID 5 disk failure, you'll have 6 remaining 2 TB drives. As the RAID controller is busily reading through those 6 disks to reconstruct the data from the failed drive, it is almost certain it will see an URE. So the read fails. And when that happens, you are one unhappy camper. The message "we can't read this RAID volume" travels up the chain of command until an error message is presented on the screen. 12 TB of your carefully protected - you thought! - data is gone. Oh, you didn't back it up to tape? Bummer!