Western digital drive confusion

[tinners]

Please can you chaps help me to try and understand the differences in the models on the current WD range of circa 500GB drives :
http://www.tinyURL.com/5afws4

Cheers.

[alexp999]

Please can you chaps help me to try and understand the differences in the models on the current WD range of circa 500GB drives :
http://www.tinyURL.com/5afws4

Cheers.

Cant really make out that screenie, extremely low quality.
Can you do another?

[tinners]

Am posting from my blackberry as no access to hexus from work so will need to wait til I get home.

I assume you clicked on the picture to make it re scale ?

Its basically a screen of all the different 500GB plus the 640GB WD drives scan sell.

Iain

[Saracen]

The first is a mainstream Caviar Blue. The second is the Green equivalent, which is a low power consumption version, hence the "Green" designation, but also supports Native Command Queueing (NCQ).

The third is the same Blue series as the first, but has 8MB of cache instead of 16MB so, in theory, should be a bit slower. The fourth is another Green low-power model, but again, the 8MB variant.

The fifth is, well, a 640MB drive, using the newer high-density platters and is reckoned to be a very fast drive.

The last one is an RE2, which is part of WD's Enterprise series. It's designed for use in RAID arrays, and comes hardware-configured in a way that assumes that it'll be use in RAID, and for extended periods. It's not really ideal for non-RAID uses, though you can reconfigure it to turn off features designed for RAID use. It does, IIRC, come with a longer warranty (5 years), and has a higher MTBF .... hence the higher price.

[alexp999]

The first is a mainstream Caviar Blue. The second is the Green equivalent, which is a low power consumption version, hence the "Green" designation, but also supports Native Command Queueing (NCQ).

The third is the same Blue series as the first, but has 8MB of cache instead of 16MB so, in theory, should be a bit slower. The fourth is another Green low-power model, but again, the 8MB variant.

The fifth is, well, a 640MB drive, using the newer high-density platters and is reckoned to be a very fast drive.

The last one is an RE2, which is part of WD's Enterprise series. It's designed for use in RAID arrays, and comes hardware-configured in a way that assumes that it'll be use in RAID, and for extended periods. It's not really ideal for non-RAID uses, though you can reconfigure it to turn off features designed for RAID use. It does, IIRC, come with a longer warranty (5 years), and has a higher MTBF .... hence the higher price.

In that case, the 640GB would be the best one IMO, I have that one . With the 320GB platters it can nearly match velociraptor transfer speeds.

Oh and the pic is working now.

[tinners]

@Saracen: great answer thanks. Will go for the 640 then.

[Zak33]

Saracen did good work there.

For the record, the RE2 is good at copying to itself, ie replicating data, and also , critically for me, have a 5 year warranty and a proper MOLEX power connector, not just a SATA power connector. But it's not quite as fast as the blue drives. I have both RE2 and SE16 (blue 16mb cache)

NCQ isn't worth a pich of snuff though so dont get carried away by it. Platter density is a good thing for performance. So you decided right

[Saracen]

If you're not using the RE2 in a RAID, Zak, I suggest getting hold of WDTLER.EXE and turning TLER (Time Limited Error Recovery) off. TLER is designed to pass drive error correction that lakes 7 seconds or longer over to the RAID controller to deal with.

This is all about whether the drive or the RAID controller handles error correction. Most RAID controllers assume that if a hard drive doesn't respond within a predetermined time, the drive has failed. A common time lapse is about 8 seconds.

Hard drives, on the other hand, have built-in error correction and, if this kicks in, it can delay the drive responding for considerably more than 8 seconds. So, for a standard drive, if EC kicks in and the drive doesn't respond in time due to it being busy with EC, the RAID controller drops it from the array, and that, of course, degrades the array. A RAID 5 array, for instance, has now lost it's redundancy and another drive failure will cost you the array. Oh, and you've probably got a lengthy array rebuild to so.

On the other hand, if TLER is enabled on a desktop drive, you've told the drive to drop it's internal EC functions after about 7 seconds, on the assumption that the RAID controller will deal with the problems to ensure no data loss. So if there's no RAID controller doing it .... well, again, you're risking data corruption.

[Zak33]

I use it in a USB caddy

[Saracen]

I use it in a USB caddy

Which means you're exposed to the data loss problem is this EC issue arises and TLER is (as by default) turned on.

My guess is that unless this drive is heavily used, it's probably a fairly small risk, but it is a risk. So I guess a crunch question is how valuable and/or critical the data on the drive is, and whether you have good backups or not?