ZFS ready drives WAS: zfs performance degradation
paul at kraus-haus.org
Fri Sep 25 14:01:29 UTC 2015
On Sep 25, 2015, at 9:11, Graham Allan <allan at physics.umn.edu> wrote:
> On 9/24/2015 7:58 PM, Paul Kraus wrote:
>> On Sep 24, 2015, at 17:40, CeDeROM <cederom at tlen.pl> wrote:
>>> For RAID/NAS use ondy WD RED drives family :-) Others WILL break
>>> timings with hidden error verify mechanisms..
>> I assume you are referring to the other “color” drives. I have had no
>> issues with the RE and SE series of Datacenter drives in zpool
> 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… 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” 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 at kraus-haus.org
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