Western Digital are one of the top three magnetic disk manufacturers and should be a safe option. The WD20EARS range was introduced in 2010, is labelled as “WD Green”, and gives you a slow rotation speed of 5900 rpm instead of 7200, with slightly lower power usage suitable for battery powered computing.
This model was obsolete almost as soon as I purchased it. Shop around for newer WD Green models.
Who?
Fast disks chew power. If you are not need that fastest disk or run on batteries, the lower power usage of the WD green range might be for you.
When?
Using the lower power WD green range in your laptop makes sense when you are not plugged into mains power or it is nighttime and your mains power is from the batteries attached to your solar powered house.
Smaller disks, 2.5" instead of 3.5", also suffer less damage when bumped, a good reason to use them in any computer small enough to be moved when switched on. The WD20EARX is unfortunately 3.5", making it unsuitable for a laptop. I bought the disk for a smaller desktop that might be pushed across the desk when some clueless person tries to dump something on my desk.
The computer will be left on long term so the lower power usage is useful.
The disk will be used for mainly reference which means the slower speed is not as big a problem.
While some disks are good for ten years, this model was obsolete almost as soon as I purchased one. If you are not in a rush to buy, look at the newer models.
There are several reasons to replace this disk in my computer as my photograph collection grows. Browsing 1 TB of photographs is too slow, a reason to replace this disk before it runs out of capacity. A 2.5" replacement is just as fast and more convenient. Any one of those reasons justifies an upgrade. The WD20EARX can be downgraded to a backup disk.
Where?
3.5" disks are limited to big desktop computers and servers. Servers use 7200 rpm disks, not 5900 rpm. USB enclosures let you use the WD20EARX as a backup but only where you can protect the disk against bumps while switched on.
Why?
Western Digital are one of the top three magnetic disk manufacturers with a market share slightly ahead of Seagate after the takeover of HGST, the old Hitachi disk business. Both WD and Seagate are double the size of Toshiba. Selecting Western Digital disks should be a safe bet.
Samsung is another big disk manufacturer but is now focused only on solid state disks. Toshiba is moving toward selling only SSD. Western Digital moved into the SSD market by buying Sandisk. The WD range of hard disks appears to be a long term investment, another reason for them to be a safe buy.
The WD green range offer lower power usage for disks switched on all day.
WD20EARX disks are nearly obsolete but have a good long life ahead. They should be a good choice for moving to low usage reference storage then to backup.
Way?
USB 3 enclosures offer a way to move the WD20EARX disks out of computers into external backup. You can also buy NAS boxes, Network Attached Storage devices, for groups of two or four disks joined together in a RAID array.
Backup software based on rsync and similar incremental copies can run in quiet times, like overnight, or in the background to copy from faster disks to the slower WD Green disks. The speed can be irrelevant with the right setup.
Worth?
For me, the capacity and speed combination was at the right price on the day of purchase. All the main brands had something similar but at a higher price. The WD green range offered lower power which will be a long term saving for a disk left on most of the time.
When the disk moves to a USB enclosure for plugging in as a backup once per week, the powered power usage is irrelevant. Reliability is the most important feature.
What?
The WD20EARS disk was introduced in 2010 and is labelled as “WD Green”. The various colours are connected to differences in price and warranty. WD Green gives you a slow rotation speed of 5900 rpm instead of 7200. The slightly lower power usage also produces slower seeks. If your computer is not battery powered, pay the little bit extra for full speed disks.
The WD20EARX-00PASB0 has a capacity of 2 TB, the largest in the WD 3.5 inch Green series way back when the series was created The disk has a buffer of 64 MB but that does nothing for the typical use of a low power “green” disk or a 2 TB capacity disk. The cache should be two or four times that size.
After you use up all the capacity of the cache buffer, the disk reads at a continuous speed of 35 MB/second, about the top end of USB 2 speed assuming your disk is in a USB enclosure and the only device on the USB path all the way through to the processor chipset. The continuous write speed is a little bit lower at 31 MB/second.
If you put the disk in a USB enclosure, use USB 3 as USB 3 has the extra bandwidth to handle peak traffic and extra traffic when the USB path is shared with other devices.
The slow WD30EARS write speed creates a very slow backup. A 1 TB notebook disk would take 9 hours with large files and closer to 15 hours for many small files. You might run the backup overnight once per month then run something like rsync each day to backup only the changed files.
Your time is too valuable to put up with that speed. Plus a WD20EARS disk is five years old (in 2016) and at end of life. Buy a replacement. A modern 2 TB 2.5” disk will use less power, produce less noise, and work at least twice as fast. Modern 2.5” disks are so efficient that you can use them in simple USB 3 cases without an external power supply. I am replacing all my older 3.5” 1 TB and 2 TB backup disks with 2.5” equivalents.
I read old reviews of this disk. They are quoting speeds up to three times more than the maximum these disks can produce. How do the testers get such stupid measurements? They use tests that run mostly in the disk cache. Imagine buying a 2 TB disk then only ever using the 64 MB cache for storage. Stupid. Stupid. You buy a 2 TB disk because you need more than 1 TB. The benchmark should use more than 1 TB.
Advanced Format
The other problem, invented by Western Digital, is the very backward “Advanced Format” used on modern disks. Disks were set to jump from the obsolete 512 byte sector format to a more modern 4096 byte sector. Western Digital introduced the fake format with 4096 byte sectors on disk emulating 512 byte sectors and called the messy result “Advanced Format”. Now we are stuck with disks that have to jump through a slow process of reading before writing. Small random writes are very slow.
The controllers in early “advanced format” disks were bad at trying to improve the mess. Some later controller chips are better at aggregating IO operations into the 4K real blocks. If you have an early AF disk, replace it with a new AF disk.
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