Choosing a SATA HD for RAID1

Choosing a SATA HD for RAID1

[Hans Malissa]

I'm trying to select suitable SATA HD for RAID1 via mdadm. I've been
reading through
https://raid.wiki.kernel.org/index.php/Choosing_your_hardware,_and_what_is_a_device%3Fand
https://raid.wiki.kernel.org/index.php/Timeout_Mismatch but I'm still
confused. I understand that I can use smartctl in order to determine
whether a drive is suitable, but what can I do to figure this out
before I purchase the drives? I've looked at
https://raid.wiki.kernel.org/index.php/Drive_Data_Sheets but I'm not
sure which information I'm looking for.
My planned mdadm RAID1 should serve to accommodate the /home
directory, so I will not need to boot from the array, and the workload
is going to be moderate. I just need to keep the data in /home secure
- I'm doing regular backups anyway, but I want to make sure that the
/home directory remains useable at all times.
The drives will be used on an openSUSE 12.3 x86_64 system with kernel
version 3.7.10 and mdadm version 3.2.6 on an Intel Desktop Board
DH67BL with SATA 6.0 Gb/s or 3.0 Gb/s. I am aware that these are
somewhat dated, but I have some specialized hardware and software
installed, and I'm therefore hesitant to update the system with newer
versions of the OS.
I'm considering Western Digital WD Gold, either 2TB (WD2005FBYZ) or
4TB (WD4003FRYZ). It says 'Enterprise Class', but I cannot find a
definitive confirmation that the drive does not suffer from the TLER
or SCT/ERC issue. Is it known whether these drives are suitable for
mdadm RAID1? Are there drives that are more suitable for my
application?
Thanks a lot,

Hans

Re: Choosing a SATA HD for RAID1

[Wols Lists]

On 29/02/20 02:47, Hans Malissa wrote:
> I'm trying to select suitable SATA HD for RAID1 via mdadm. I've been
> reading through
> https://raid.wiki.kernel.org/index.php/Choosing_your_hardware,_and_what_is_a_device%3Fand
> https://raid.wiki.kernel.org/index.php/Timeout_Mismatch but I'm still
> confused. I understand that I can use smartctl in order to determine
> whether a drive is suitable, but what can I do to figure this out
> before I purchase the drives? I've looked at
> https://raid.wiki.kernel.org/index.php/Drive_Data_Sheets but I'm not
> sure which information I'm looking for.

Basically, any drive in an X.1 section that says "Raid drives" is suitable.

> My planned mdadm RAID1 should serve to accommodate the /home
> directory, so I will not need to boot from the array, and the workload
> is going to be moderate. I just need to keep the data in /home secure
> - I'm doing regular backups anyway, but I want to make sure that the
> /home directory remains useable at all times.

> The drives will be used on an openSUSE 12.3 x86_64 system with kernel
> version 3.7.10 and mdadm version 3.2.6 on an Intel Desktop Board
> DH67BL with SATA 6.0 Gb/s or 3.0 Gb/s. I am aware that these are
> somewhat dated, but I have some specialized hardware and software
> installed, and I'm therefore hesitant to update the system with newer
> versions of the OS.

JUST MAKE SURE YOU UPDATE MDADM TO THE LATEST VERSION !!! As a pure
linux program, downloading and installing it from the official sources
is dead easy. You're unlikely to hit problems with the old version but
there have been a LOT of bugs fixed since then that regularly give grief
on the mailing list.

> I'm considering Western Digital WD Gold, either 2TB (WD2005FBYZ) or
> 4TB (WD4003FRYZ). It says 'Enterprise Class', but I cannot find a
> definitive confirmation that the drive does not suffer from the TLER
> or SCT/ERC issue. Is it known whether these drives are suitable for
> mdadm RAID1? Are there drives that are more suitable for my
> application?

I notice that the WD RE4 drive is listed with almost exactly the same
model number you give. It also looks like these drives are known as WD
Gold, so it's extremely likely the drives you are looking at are okay.

Are you in the EU? Certainly in the UK, if I was ordering these drives,
I would do so "in person" and say that they MUST support SCT/ERC. If
they don't, that would give me the right to return them as unsuitable.
And if you buy them mail order, you should also have the right to return
them as unsuitable (especially if they're described as "enterprise").

> Thanks a lot,
> 
I notice you say they are for a raid-1. SCT/ERC isn't that important for
data integrity with a raid 1 because each drive can stand on its own.
Once the data is scattered across multiple drives, that's when you
really need it - if you want to go raid 5 or 6 at some point that's when
you'll wish you'd bought drives that support it.

And on a personal note I'd go for the 4GB drives. I doubt they're much
more expensive, and you won't have to worry about expansion for a lot
longer. I'm outgrowing my 3GB Barracudas (yes I made the mistake of
buying non-SCT/ERC drives), and switching to 4GB Ironwolves.

And if you do upgrade your kernel I would look at throwing dm-integrity
into the mix. It's been around a while but I would be very hesitant at
suggesting it for your ancient setup.

Cheers,
Wol

Re: Choosing a SATA HD for RAID1

[Wols Lists]

On 29/02/20 10:19, Renaud (Ron) OLGIATI wrote:
> On Sat, 29 Feb 2020 09:18:29 +0000
> Wols Lists <antlists@youngman.org.uk> wrote:
> 
>> On 29/02/20 02:47, Hans Malissa wrote:
>>> I'm trying to select suitable SATA HD for RAID1 via mdadm. 
> 
> As an aside on this thread, should one aim to build RAID arrays from HDs of the same make and model, or on the contrary diversify HDs in the hope that disks of different makers and model are less likely to fail at the same time ?
>  
It's widely accepted that you should not buy all your raid disks at the
same time from the same manufacturer, precisely because they will
probably all suffer from similar defects.

Drives tend to fail quickly from defects, or wear out slowly from use.
Especially in a raid array where usage patterns are very similar, that
means you don't want similar drives with similar usage as they'll wear
out together.

Throw in the fact that rebuilding an array regularly stresses the other
drives to the point of failure ...

So no. Don't buy your drives in one hit. Either spread them out over
time, or mix models and manufacturers. With that said, a home user like
me is more likely to deliberately retire a drive than have it fail, so
from my point of view it's pretty irrelevant. And nowadays, with good
quality drives, that's also true for many companies - if an enterprise
drive comes with a five-year warranty and you expect to retire the drive
because it's become too small in five years time, well, the probability
that they'll all fail together is too small to worry about. The
probability that ONE drive will fail is tiny, let alone more ...

Cheers,
Wol

Re: Choosing a SATA HD for RAID1

[Hans Malissa]

On Sat, Feb 29, 2020 at 2:18 AM Wols Lists <antlists@youngman.org.uk> wrote:
> I notice that the WD RE4 drive is listed with almost exactly the same
> model number you give. It also looks like these drives are known as WD
> Gold, so it's extremely likely the drives you are looking at are okay.

Thanks a lot for this information. WD's product names are confusing;
could it be that Gold is a newer version of the RE?
Greetings,

Hans

Re: Choosing a SATA HD for RAID1

[antlists]

On 29/02/2020 18:08, Hans Malissa wrote:
> On Sat, Feb 29, 2020 at 2:18 AM Wols Lists <antlists@youngman.org.uk> wrote:
>> I notice that the WD RE4 drive is listed with almost exactly the same
>> model number you give. It also looks like these drives are known as WD
>> Gold, so it's extremely likely the drives you are looking at are okay.
> Thanks a lot for this information. WD's product names are confusing;
> could it be that Gold is a newer version of the RE?
> Greetings,
>
Dunno. It wouldn't surprise me if RE was engineering's name, and Gold 
was marketing's name.

Cheers,

Wol