HDD duty cycle, WD's "AV" HDDs for 24/7 apps

[fffblackmage]

I didn't get much of a reply in the memory/storage subforum, so I thought I'd try asking here instead:

Most consumer HDDs are made for normal use. Basically, the computer is turned on during the day, and turned off at night. So the typical duty cycle of the HDD is only a few to several hours in a given 24-hour day.

Just recently, I noticed that WD makes a series of HDDs for 24/7 use (these).

My question is: placing both types of HDDs in the same environment, some sort of 24/7 application like a NAS or DVR, how does WD's designed-for-24/7-use HDDs compare to traditional HDDs? Are they more durable or reliable? Or is this simply a marketing gimmick?

 

[C1]

Dont know abou WD, but they probably do similarly what other manufactures do for their enterprise drives. Looking at the Hitachi spec sheets tells a lot of what you want to know. Enterprise drives:
- Error rate is an order of magnitude less
- Tolerances are tighter
- Testing is more rigorous
- Warranty is greater (5 yrs typical)
- Operational ranges are wider (temp, humidity, continuous running hours, shock, vibration levels, etc.)

Hitachi's enterprise drives are not just the regular drives but with just a 5 yr warranty (versus one or three).

 

[Mark R]

They are similar drives mechanically - but often lower speed drives (e.g. 5400 or 5900 rpm), in order to reduce heat, power consumption and noise. They may also come with 'acoustic management' set to 'minimum performance, minimum noise' mode - whereas normal drives tend to come from the factory set to 'maximum performance' mode.

They also have different firmware installed. The cache is configured to behave differently. Conventional hard drives tend to cache data that has already been read in case the OS requires it again, and only 'anticipate' (read ahead) a small amount of data without being asked. AV HDs minimize caching of files that have been requested (because in a streaming video, rewinding is relatively uncommon, and good performance while rewinding isn't very important) and maximize 'anticipatory' reading (to ensure the smoothest possible playback).

Additionally, they may use more aggressive write caching, which may mean less data integrity in case of power failure (but provide special mechanisms to ensure critical data is securely saved).

There is also different weak or bad sector handling. If a normal drive has problems reading a sector, it will try over and over again, using many different error recovery techniques to try to recover the data - this can result in the drive becoming unresponsive for several minutes. For AV streaming, if a frame is corrupted it's doesn't really matter (the playback gets a few corrupted pixels/static but it can keep playing), instead what really matters is that the drive stays responsive (otherwise recordings might fail), and so that playback can continue (even if it's a bit glitchy). As a result, AV drives abandon data recovery attempts from 'weak' sectors very early, because they assume that individual sectors of data are of low value.

 

[VirtualLarry]

I've never had a problem running my drives 24/7 for years at a time.

 

[mfenn]

They are similar drives mechanically - but often lower speed drives (e.g. 5400 or 5900 rpm), in order to reduce heat, power consumption and noise. They may also come with 'acoustic management' set to 'minimum performance, minimum noise' mode - whereas normal drives tend to come from the factory set to 'maximum performance' mode.

They also have different firmware installed. The cache is configured to behave differently. Conventional hard drives tend to cache data that has already been read in case the OS requires it again, and only 'anticipate' (read ahead) a small amount of data without being asked. AV HDs minimize caching of files that have been requested (because in a streaming video, rewinding is relatively uncommon, and good performance while rewinding isn't very important) and maximize 'anticipatory' reading (to ensure the smoothest possible playback).

Additionally, they may use more aggressive write caching, which may mean less data integrity in case of power failure (but provide special mechanisms to ensure critical data is securely saved).

There is also different weak or bad sector handling. If a normal drive has problems reading a sector, it will try over and over again, using many different error recovery techniques to try to recover the data - this can result in the drive becoming unresponsive for several minutes. For AV streaming, if a frame is corrupted it's doesn't really matter (the playback gets a few corrupted pixels/static but it can keep playing), instead what really matters is that the drive stays responsive (otherwise recordings might fail), and so that playback can continue (even if it's a bit glitchy). As a result, AV drives abandon data recovery attempts from 'weak' sectors very early, because they assume that individual sectors of data are of low value.

Great post! :thumbsup:

 

[fffblackmage]

Dont know abou WD, but they probably do similarly what other manufactures do for their enterprise drives. Looking at the Hitachi spec sheets tells a lot of what you want to know. Enterprise drives:
...
Hitachi's enterprise drives are not just the regular drives but with just a 5 yr warranty (versus one or three).

Unfortunately, I don't believe these "AV" drives are of the enterprise/server kind. For one thing, they're too damn cheap to be enterprise-grade or even close. Rather, they appear more like normal consumer-grade HDDs, but with the "24/7" label slapped on it.

...

Awesome post, very informative! Thanks!

I've never had a problem running my drives 24/7 for years at a time.

I'm glad to hear that!



I was mostly concerned about differences in reliability, but it seems like the differences in firmware Mark R brought up seems like the most probable answer.