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Date:      Fri, 25 Sep 2015 10:01:18 -0400
From:      Paul Kraus <paul@kraus-haus.org>
To:        Graham Allan <allan@physics.umn.edu>
Cc:        freebsd-questions@freebsd.org
Subject:   ZFS ready drives WAS: zfs performance degradation
Message-ID:  <106217D9-F3DB-4DB5-822E-098041B5BC6F@kraus-haus.org>
In-Reply-To: <5605481D.10902@physics.umn.edu>
References:  <56019211.2050307@dim.lv> <37A37E9D-9D65-4553-BBA2-C5B032163499@kraus-haus.org> <56038054.5060906@dim.lv> <782C9CEF-BE07-4E05-83ED-133B7DA96780@kraus-haus.org> <56040150.90403@dim.lv> <60BF2FC3-0342-46C9-A718-52492303522F@kraus-haus.org> <560412B2.9070905@dim.lv> <8D1FF55C-7068-4AB6-8C0E-B4E64C1BB5FA@kraus-haus.org> <56042209.8040903@dim.lv> <2008181C-F0B5-4581-9D15-11911A1DE41B@kraus-haus.org> <CAFYkXjkdUrcUUdVQW4qgSuEmtifD=mvbvf4k0vq5t9R6dtR1pQ@mail.gmail.com> <6498A090-A2A2-4580-A148-2BCBF68BF2BF@kraus-haus.org> <5605481D.10902@physics.umn.edu>

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On Sep 25, 2015, at 9:11, Graham Allan <allan@physics.umn.edu> wrote:

> On 9/24/2015 7:58 PM, Paul Kraus wrote:
>> On Sep 24, 2015, at 17:40, CeDeROM <cederom@tlen.pl> wrote:
>>=20
>>> For RAID/NAS use ondy WD RED drives family :-) Others WILL break
>>> timings with hidden error verify mechanisms..
>>>=20
>>> http://www.wdc.com/red
>>=20
>> I assume you are referring to the other =93color=94 drives. I have =
had no
>> issues with the RE and SE series of Datacenter drives in zpool
>> configurations.
>=20
> WD Reds are pretty solid, and I have used hundreds of them in ZFS =
pools without *apparent* issues, while I would never consider the blue =
or even less Green for this. However they're still a low-cost option - =
if I'd had the funds I would much rather have used SE or RE!

Your comment reminded me=85 one of the big reasons to only use =
Enterprise / Datacenter / NAS rated drives for ZFS is the way the =
_drive_ handles errors. Many of the consumer drives will retry a failing =
READ many, many times. This _can_ lead to timeout issues in the OS and =
ZFS. The reasoning here is that for a consumer, getting a good read is =
worth the extra time (I have seen reports of up to 30 seconds before =
giving up) because the consumer probably does not have any redundancy. =
With ZFS (assuming something more than a basic stripe configuration) you =
want the drive to return the read error to the OS as fast as it can so =
that the OS and ZFS can deal with it.

I have also used WD Green and Purple drives with ZFS, but I do not =
expect Enterprise grade operation out of them.

I also question the economics of the consumer drives, once you take the =
5 year warranty in account.

Looking at Newegg for 2 TB 3.5=94 WD drives:

Green $79 2-year
Purple $85 3-year
Red NAS $90 3-year
Black $119 5-year
SE $130 5-year
Red Pro NAS $134 5-year
RE $153 5-year

So the premium cost for the Red NAS is $11 over the cheapest option.

The premium cost for a 5-year warranty (Black, not rated for 24/7 or =
NAS, a high end desktop drive) is $40.

The Premium for the cheapest Datacenter drive (SE) is $51, or more than =
a 50% increase in cost. But the warranty is more than twice as long =
(2-year vs. 5-year).

In my experience, most 5-year warranty drives fail in some way during =
the warranty period. This is especially true of Seagate. On my home =
system, 5 out of 6 Seagate ES.2 series drives failed within 5 years, the =
last one failed within 6 months of the warranty expiration. Half of my =
HGST drives have failed under warranty (so far, they have not all hit =
end of warranty yet), none of my WD RE or SE series have failed, but =
they are the youngest drives in my collection.

So part of what I am paying for with the Datacenter drives is the =
knowledge that I will NOT have to pay to replace that drive for 5 years.

--
Paul Kraus
paul@kraus-haus.org




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