32 MB vs 64 MB and 3 GB/s vs 6 GB/s

[decrescendo]

Will I really notice the difference between a 32 MB cache 7200 RPM drive and a 64 MB cache 7200 RPM drive?

Additionally, would I notice a difference between two similar drives if only their SATA interface speed was 3 GB/s versus 6 GB/s?

Cutting to the chase, I'm looking to buy a few 1+ TB hard drives for a media center Win7 machine.

The machine would be doing the following:
1. store ~4TB of mp3s, movies, photos, and documents (probably 2x2TB drives)
2. stream audio to Win7 laptop-connected or Squeezebox-connected speakers
3. stream 1080p video to an HTPC-connected TV
4. be constantly running uTorrent
5. ability to rip optical discs (Blu-Ray, DVD)
6. function as backup computer in case laptop breaks
7. store backup image of laptop

Other attributes:
8. Will sit in a corner of my living room or bedroom without being connected to a keyboard or monitor.
9. The data on it will probably be backed up to some sort of NAS or set of USB drives.

It's easy to buy a few 7200 RPM 64 MB cache, 6 GB/s SATA drives, but what type of thing would I have to be doing to actually NOTICE that speed?

Could I back these drives down to a "green" 5600 RPM speed and still carry out the same tasks?

Any help would be great. Thanks!

 

[Mr. Pedantic]

Not really, and not really.

And yes, a 5400rpm drive would do pretty much as well. Basically the cheaper the better for your purposes.

 

[decrescendo]

Not really, and not really.

And yes, a 5400rpm drive would do pretty much as well. Basically the cheaper the better for your purposes.

and higher RPM = higher heat, right?

Is backing off the RPM number the only thing that differentiates "green" drives from performance drives?

 

[fffblackmage]

There's firmware too. Noise, seek latency, and I/O performance is different depending on how aggressive you want the arms to move around seeking data.

If you're looking for HDDs for a NAS or USB enclosure, there's really no point in getting high-performance HDDs. You'll be bottlenecked by USB or network transmission mediums.

 

[decrescendo]

There's firmware too. Noise, seek latency, and I/O performance is different depending on how aggressive you want the arms to move around seeking data.

If you're looking for HDDs for a NAS or USB enclosure, there's really no point in getting high-performance HDDs. You'll be bottlenecked by USB or network transmission mediums.

These drives would go in my Windows 7 box.

I suppose I'd only be bottlenecked there if I ended up with a motherboard that allowed 3 GB/s and hard drives that were 6 GB/s.

 

[Soulkeeper]

3 Gb/s vs. 6 Gb/s for mechanical drives is a non issue

 

[decrescendo]

3 Gb/s vs. 6 Gb/s for mechanical drives is a non issue

As in you really can't even tell the difference between them?

 

[Elixer]

As in you really can't even tell the difference between them?

Yep, pretty much. They just don't spin fast enough (and/or the platters aren't dense enough) to get anywhere close to that, unless you do some RAID setup.

Just get a bunch of 5400RPM drives (aka 'green') and you should be set.
Only the OS drive should be 7200RPM or a SSD.

 

[Mr. Pedantic]

These drives would go in my Windows 7 box.

Unless you're using these drives as an OS drive, you would honestly be hard put to tell the difference, I reckon.

As in you really can't even tell the difference between them?

Not even in most benchmarks. SATA III drives will burst a tiny bit higher, and higher cache will mean it can burst for a tiny bit longer, but the difference is negligible. SATA III for HDDs is mainly a marketing gimmick.

 

[decrescendo]

Unless you're using these drives as an OS drive, you would honestly be hard put to tell the difference, I reckon.


Not even in most benchmarks. SATA III drives will burst a tiny bit higher, and higher cache will mean it can burst for a tiny bit longer, but the difference is negligible. SATA III for HDDs is mainly a marketing gimmick.

So is it worth getting an SDD for the OS given the machine will be doing what I listed in the original post?

Otherwise, I guess I could buy a smaller third 7200 rpm HDD for the OS and then use the two large green HDDs for data storage.

 

[aigomorla]

If you're looking for HDDs for a NAS or USB enclosure, there's really no point in getting high-performance HDDs. You'll be bottlenecked by USB or network transmission mediums.

Sorry to hijack the thread but i had a simular question.

I am preping to setup a 8TB Raid 5 Array on a Dedicated Raid Controller.
The server will act like a NAS basically.

I heard a lot of no no's in regards to WD green drives and RAID.

Do i really need to get the caviar blacks / RE's?
Most of the stuff on it will be backup + Media files, so i dont need the insane write / read speed.

 

[fffblackmage]

These drives would go in my Windows 7 box.

I suppose I'd only be bottlenecked there if I ended up with a motherboard that allowed 3 GB/s and hard drives that were 6 GB/s.

Well, these HDDs are going into a NAS box that will stream stuff to your HTPC and whatever else, right?

How fast is your network? If you plan on streaming over wireless, you're limited to 150 mbps (for wireless N), at best ? That's less than 19 MBps (don't forget there's also overhead). If you're lucky to have things wired, then you can easily get a Gigabit network set up.

Hm.... 1Gbps network. That's quite slow compared to SATA 3Gbps and 6Gbps, isn't it?

Then there's the actual speed of the HDDs themselves. SATA 3Gbps and 6Gbps are just a transmission medium. The HDDs themselves aren't actually capable of reading/writing that much data that fast. The fastest HDD probably can transfer about 150MBps (1.2 Gbps), that's only about half of what SATA II, or SATA 3Gbps, can offer.

Sorry to hijack the thread but i had a simular question.

I am preping to setup a 8TB Raid 5 Array on a Dedicated Raid Controller.
The server will act like a NAS basically.

I heard a lot of no no's in regards to WD green drives and RAID.

Do i really need to get the caviar blacks / RE's?
Most of the stuff on it will be backup + Media files, so i dont need the insane write / read speed.

I'm no expert on this subject, but AFAIK, you'll need those "RE" HDDs for hardware RAID, because of TLER.

From what I understand, HDDs may spend time trying to read a weak sector (or for whatever other reason). During that time, they are unresponsive, so the RAID controller may think that the HDD died, dropping it out of the RAID array. This may be why those WD Green drives aren't recommended for RAID set-ups.

 

[aigomorla]

I'm no expert on this subject, but AFAIK, you'll need those "RE" HDDs for hardware RAID, because of TLER.

From what I understand, HDDs may spend time trying to read a weak sector (or for whatever other reason). During that time, they are unresponsive, so the RAID controller may think that the HDD died, dropping it out of the RAID array. This may be why those WD Green drives aren't recommended for RAID set-ups.

crap that was what i was worried about...
As the price difference is almost double on a green vs RE :\

And i dont think i will need that speed cuz most of the file transfers will be done via network. :\
I wanted Raid5 for the fault saving. :\

 

[decrescendo]

Well, these HDDs are going into a NAS box that will stream stuff to your HTPC and whatever else, right?

How fast is your network? If you plan on streaming over wireless, you're limited to 150 mbps (for wireless N), at best ? That's less than 19 MBps (don't forget there's also overhead). If you're lucky to have things wired, then you can easily get a Gigabit network set up.

Hm.... 1Gbps network. That's quite slow compared to SATA 3Gbps and 6Gbps, isn't it?

Then there's the actual speed of the HDDs themselves. SATA 3Gbps and 6Gbps are just a transmission medium. The HDDs themselves aren't actually capable of reading/writing that much data that fast. The fastest HDD probably can transfer about 150MBps (1.2 Gbps), that's only about half of what SATA II, or SATA 3Gbps, can offer.


I'm no expert on this subject, but AFAIK, you'll need those "RE" HDDs for hardware RAID, because of TLER.

From what I understand, HDDs may spend time trying to read a weak sector (or for whatever other reason). During that time, they are unresponsive, so the RAID controller may think that the HDD died, dropping it out of the RAID array. This may be why those WD Green drives aren't recommended for RAID set-ups.

I've always wondered about why green drives weren't recommended for RAID but that makes perfect sense.

Also, I plan on having mostly everything in my apartment hardwired, especially the connection between this media center box and my HTPC. And, yes, these drives would be in a Win7 box that stores all of my movies.

 

[fffblackmage]

Found this old post:

Posted 10 January 2011
Original url: http://forums.storagereview.com/ind...t-tlererccctl/page__view__findpost__p__266337

Both Linux and FreeBSD can use normal desktop drives without TLER, and in fact you would not even want TLER in such a case, since TLER can be dangerous in some circumstances. Read on.


What is TLER/CCTL/ERC?
TLER (Time-Limited Error Recovery
CCTL (Command Completion Time Limit)
ERC (Error Recovery Control)

These basically mean the same thing: limit the number of seconds the harddrive spends on trying to recover a weak or bad sector. TLER and the other variants are typically configured to 7 seconds, meaning that if the drive has not managed to recover that sector within 7 seconds, it will give up and forfeit recovery, and return an I/O error to the host instead.

The behavior without TLER is that up to 120 seconds (20-60 is more frequent) may pass before a disk gives up recovery. This behavior causes haywire on all Hardware RAID and Windows-based software/onboard/driver RAIDs. The RAID consider typically is configured to consider disks that don't respond in 10 seconds as completely failed; which is bizarre to say the least! This smells like the vendors have some sort of deal causing you to buy HDDs at twice the price just for a simple firmware fix. LOL!! Don't get yourself buttraped; read on!


When do i need TLER?
You need TLER-capable disks when using any Hardware RAID or any Windows-based software RAID; bummer if you're on Windows platform! But this also means Hardware RAID on any OS (FreeBSD/Linux) would also need TLER disks; even when configured to run as 'JBOD' array. There may be controllers with different firmware that allow you to set the timeout limit for I/O; but i've not yet heard about specific products, except some LSI 1068E in IR mode; but reputable vendors like Areca (FW1.43) certainly require TLER-enabled disks or they will drop-out like candy whenever you encounter a bad/weak sector that needs longer recovery than 10 seconds.

Basically, if you use a RAID platform that DEMANDS the disks to respond within 10 seconds, and will KICK OUT disks that do not respond in time, then you need TLER.


When don't i need TLER?
When using FreeBSD/Linux software RAID on a HBA controller; which is a RAID-less controller. Areca HW RAID running in JBOD mode is still a RAID controller; it controls whether the disks are detached, not the OS. With a true HBA like LSI 1068E (Intel SASUC8i) your OS would have control about whether to detach the disk or not; and Linux/BSD won't, at least not for a simple bad sector. Not sure about Apple OSX actually, but since it's based on FreeBSD i could speculate that it would have the same behavior as FreeBSD; perhaps tuned differently.


Why don't you want TLER even if your disks are capable?
If you don't need TLER, then you don't want TLER! Why? Well because TLER is dangerous! Nonesense? Consider this:

1. You have a nice RAID5 array on Hardware RAID, being a valuable customer you spent the premium price on TLER capable disks.
2. Now one of your disk dies; oh bummer! But hey i have RAID5; i' protected, RIGHT?
3. So i buy a new disk, and replace the failed one! So easy, ha ha!
4. Oh noooes! A bad sector on of the remaining member disks, and it caused TLER to forfeit; now i got an I/O error during rebuilding my degraded array and the rebuild stopped and i lost access to my data! Arrrrgh!!

The danger in TLER lies that if you lost your redundancy, then if a weak sector occurs that COULD be recovered, TLER will force the drive to STOP TRYING after 7 seconds. If it didn't fix it by then, and you lost your redundancy, then TLER is a harmful property instead of a useful one.

TLER works best when you got alot of redundancy and can swap disks easily, and want disks that show any sign of weakness - if even just a fart - to be kicked out and replaced ASAP, without causing hickups which are unacceptable to a heavy-duty online money transaction server, for example. So TLER can be useful, but for consumers this is more like an interesting way for vendors to make some more money from you poor souls!


What is Bit-Error Rate and how does it relate to TLER?
uBER or Uncorrectable Bit-Error Rate, has been steady at 10^-14, but capacities are growing and the BER rate stays the same. That means that modern high-capacity harddrives now are more likely to be affected by amnesia; they sometimes really cannot read a sector. This could be physical damage to the sector itself, or just a weak charge meaning no physical damage to that sector but just unreadable.

So 2TB 512-byte sector disks have a relative high BER rate. This makes them even more susceptible to dropping out of conventional Windows/Hardware RAIDs, and is why the TLER feature has become more important. But i consider it to be rather a curse than a blessing.


So.. explain again please; Why don't i need TLER on Linux/BSD?
Simple: the OS does not detach a disk that times out, but resets the interface and re-tries the I/O. Also when using ZFS, it will write to a bad sector, causing that bad sector to be instantly fixed/healed/corrected since writing to a bad sector makes the disk perform a sector swap right away. In the SMART data, the "Current Pending Sector" (active bad sector) would then become "Reallocated Sector Count" (passive bad sector which no longer causes harm and cannot be seen or used by the host Operating System anymore).


That includes ZFS?
Yes. ZFS is, of course, the most reliable and advanced filesystem you can use to store your files, right now. It's free, it's available, it's hot. So use it whenever you can.

 

[aigomorla]

CRAP so from my research, whats more important then 3G / 6G 32MEG / 64MEG

is it RAID5 possible? Yes or No..

LOL..

Meh anyone know of 2TB drives which cost less then 100 dollars that i can put 5 in Raid 5 and not have to worry about TLER barfing my Raid array?

 

[decrescendo]

Ok, well I'll probably go for some cheaper-is-better high capacity (1+ TB) drives for my media storage. I would imagine these would be "green" drives to cut down on heat AND price.

For my OS drive, I'll go for something that's 7200RPM. I would imagine I could then buy something with a relatively small capacity if it's just going to be for the OS in order to cut down cost here, too.

Sound logical?