"raid" versions of hard drives for software raid?

"raid" versions of hard drives for software raid?

[Dan Christensen]

I'm looking at either the Western Digital 500G RE2 drives or the cheaper
500G SE16 drives.  I have read that for use with a hardware raid card,
the RE2 drives are more appropriate, and I'm wondering if the same is
true for software raid.

I am planning to get two drives, and may use the entire drives as RAID1,
or I might partition the drives and use most of the partitions in a
RAID1 configuration, but leave a few of the partitions without RAID.

Suggestions appreciated (even suggestions for another drive I should
consider).

I do like the 5 year warranty on the RE2 drives and the increased MTBF,
as I do have a long history of drive failures...

Thanks,

Dan

Re: "raid" versions of hard drives for software raid?

[Brendan Conoboy]

Dan Christensen wrote:
> I'm looking at either the Western Digital 500G RE2 drives or the cheaper
> 500G SE16 drives.  I have read that for use with a hardware raid card,
> the RE2 drives are more appropriate, and I'm wondering if the same is
> true for software raid.

It's a mechanical property- vibration tolerance and whatnot.  No 
difference between software and hardware raid in this sense.

> I am planning to get two drives, and may use the entire drives as RAID1,
> or I might partition the drives and use most of the partitions in a
> RAID1 configuration, but leave a few of the partitions without RAID.
> 
> Suggestions appreciated (even suggestions for another drive I should
> consider).
> 
> I do like the 5 year warranty on the RE2 drives and the increased MTBF,
> as I do have a long history of drive failures...

I have 5 400GB RE2 drives in a RAID5 array (software raid, naturally). 
That 5 year warranty has come in handy- only 1 of the original drives 
still remains.  5 RMAs in under 3 years.  Maybe the 500GB is better.

-- 
Brendan Conoboy / Red Hat, Inc. / blc@redhat.com

Re: "raid" versions of hard drives for software raid?

[Justin Piszcz]

On Wed, 2 Jul 2008, Brendan Conoboy wrote:

> Dan Christensen wrote:
>> I'm looking at either the Western Digital 500G RE2 drives or the cheaper
>> 500G SE16 drives.  I have read that for use with a hardware raid card,
>> the RE2 drives are more appropriate, and I'm wondering if the same is
>> true for software raid.
>
> It's a mechanical property- vibration tolerance and whatnot.  No difference 
> between software and hardware raid in this sense.
>
>> I am planning to get two drives, and may use the entire drives as RAID1,
>> or I might partition the drives and use most of the partitions in a
>> RAID1 configuration, but leave a few of the partitions without RAID.
>> 
>> Suggestions appreciated (even suggestions for another drive I should
>> consider).
>> 
>> I do like the 5 year warranty on the RE2 drives and the increased MTBF,
>> as I do have a long history of drive failures...
>
> I have 5 400GB RE2 drives in a RAID5 array (software raid, naturally). That 5 
> year warranty has come in handy- only 1 of the original drives still remains. 
> 5 RMAs in under 3 years.  Maybe the 500GB is better.

That's a lot of RMA's, bad PSU or vibration issues, or a bad lot of 
drives?

Re: "raid" versions of hard drives for software raid?

[Dan Christensen]

Brendan Conoboy <blc@redhat.com> writes:

> Dan Christensen wrote:
>> I'm looking at either the Western Digital 500G RE2 drives or the cheaper
>> 500G SE16 drives.  I have read that for use with a hardware raid card,
>> the RE2 drives are more appropriate, and I'm wondering if the same is
>> true for software raid.
>
> It's a mechanical property- vibration tolerance and whatnot.  No
> difference between software and hardware raid in this sense.

The difference that is most commonly described, and that I should have
highlighted, is TLER: Time-Limited Error Recovery.  Apparently, the SE16
drives can take a long time to recover from an error (up to two minutes,
I believe), and hardware raid controllers can kick the drives out of the
array when it would instead be better for the drive to return a
read/write error and let the raid controller deal with it.

My question is really whether this logic applies to linux software raid.

One other point is that I also read that TLER can be enabled and
disabled for both SE16 and RE2 drives using Windows software.  Not sure
if it runs under wine.  See

  http://www.hardforum.com/archive/index.php/t-1285254.html

Dan

Re: "raid" versions of hard drives for software raid?

[Brendan Conoboy]

Justin Piszcz wrote:
> That's a lot of RMA's, bad PSU or vibration issues, or a bad lot of drives?

My educated case is that it was a bad batch of drives (Bought them 
sooner after their introduction).  Drives in the enclosure from other 
MFR's have held up reliably and heat has been a non-issue.

Dan might want to see if hdparm has a tunable for the TLER setting he's 
concerned about.  Modern mdadm versions will attempt to rewrite a sector 
if there's a read error using parity or mirrors to reconstruct the data. 
  For this purpose having a short timeout before getting an error would 
be preferable to waiting a couple minutes.

-- 
Brendan Conoboy / Red Hat, Inc. / blc@redhat.com

Re: "raid" versions of hard drives for software raid?

[Dan Christensen]

Dan Christensen <jdc@uwo.ca> writes:

>> Dan Christensen wrote:
>>> I'm looking at either the Western Digital 500G RE2 drives or the cheaper
>>> 500G SE16 drives.  I have read that for use with a hardware raid card,
>>> the RE2 drives are more appropriate, and I'm wondering if the same is
>>> true for software raid.
>
> The difference that is most commonly described, and that I should have
> highlighted, is TLER: Time-Limited Error Recovery.  Apparently, the SE16
> drives can take a long time to recover from an error (up to two minutes,
> I believe), and hardware raid controllers can kick the drives out of the
> array when it would instead be better for the drive to return a
> read/write error and let the raid controller deal with it.
>
> My question is really whether this logic applies to linux software raid.

One more reference:

  http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery

It certainly sounds to me like TLER is also appropriate for software
raid, so I'm going to go ahead and get the RE2 drives.

Dan

Re: "raid" versions of hard drives for software raid?

[Roger Heflin]

Dan Christensen wrote:
> Dan Christensen <jdc@uwo.ca> writes:
> 
>>> Dan Christensen wrote:
>>>> I'm looking at either the Western Digital 500G RE2 drives or the cheaper
>>>> 500G SE16 drives.  I have read that for use with a hardware raid card,
>>>> the RE2 drives are more appropriate, and I'm wondering if the same is
>>>> true for software raid.
>> The difference that is most commonly described, and that I should have
>> highlighted, is TLER: Time-Limited Error Recovery.  Apparently, the SE16
>> drives can take a long time to recover from an error (up to two minutes,
>> I believe), and hardware raid controllers can kick the drives out of the
>> array when it would instead be better for the drive to return a
>> read/write error and let the raid controller deal with it.
>>
>> My question is really whether this logic applies to linux software raid.
> 
> One more reference:
> 
>   http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery
> 
> It certainly sounds to me like TLER is also appropriate for software
> raid, so I'm going to go ahead and get the RE2 drives.
> 
> Dan

If you were trying to salvage as much data as possible off of a drive TLER would 
also be nice, since it would lower the time to get a bad sector error.

I don't really understand how much use it is to try that many times, the drive 
should be able to try 1x per rev, so at 7200, 120 times per second, I would 
wonder how many times that they get a good read after having failed the first 
120 times, much less after the first 7 seconds (960 failures) of trying, or even 
longer periods without TLER.

In fact I would think for a RAID drive one would want even lower than 7 seconds.

                                 Roger