[ale] Best 2TB drives to extend my RAID array?

[Greg Freemyer]

On Thu, Mar 3, 2011 at 1:02 PM, Derek Atkins <warlord at mit.edu> wrote:
>> On Thu, 2011-03-03 at 09:46 -0500, I wrote:
>>> My 1.8TB RAID(10) array is close to filling, and I'm looking to buy
>>> some additional drives to extend it.  I was thinking that I'd buy a
>>> pair of 7200RPM 2TB drives to effectively double my raid size, which
>>> should last me several years at the current usage rate.  Anyone have
>>> recommendations for currently-available drives?  All else bring equal
>>> I'm thinking about buying this drive:
>>>
>>>   http://www.newegg.com/Product/Product.aspx?Item=N82E16822145473
>>>
>>> Has anyone else been in the market for large drives and/or have
>>> opinions?
>
> scott <scott at sboss.net> writes:
>> I have been buying Seagate 2TB SATA drives for ~$79 from NewEgg.
>> Seagates seem to work very well. And their customer service team is
>> very responsive if you have issues.
>
> The $79 Seagate drives appear to be 5400RPM, not 7200RPM.  The cheapest
> 2TB 7200RPM Seagate is $170.  I'd prefer to stay with 7200RPM drives, I
> think, for speed.
>
> "Michael B. Trausch" <mike at trausch.us> writes:
>> Just keep in mind that HDDs have the same failure rates (in terms of the
>> physical platters) as similar drives of smaller capacity in the last
>> several years.  That means that the probability that you will encounter
>> significant errors is vastly increased.
>>
>> An error in the physical space that 1 sector took up in a 120 GB drive
>> is likely to be an error that sits in the space of a great many sectors
>> on a 2 TB drive.  It's unlikely that the spare sectors area is much
>> larger than in older drives, as well, though I cannot say for sure
>> either way.
>
> Sure, but that's also why you run RAID and smart.  I've currently got
> four 1TB drives in my array and haven't had any errors, yet.  But I
> suspect it's getting close to the time where I need to think about
> proactively replacing them.

Maybe.

With 2 TB drives the "Bit error rate" or whatever they call it starts
to be meaningful.  I believe a drive in spec. has a 1 in 17 chance of
having some bad sectors on it.  (You can do the math from the spec.)

So if/when your first drive fails, there is a 1 in 17 chance of there
being none-recoverable data on the surviving drive.

I don't know if raid1 will continue a rebuild after hitting a media
error or not.

For another $120, you can do a 3-disk raid 1.  mdraid supports that.
Much safer with huge drives.

Greg