READ THE DOCUMENTATION THOROUGHLY on these SMR drives.   There are serious 
WRITE restrictions on these drives because of the overlapping (shingled) 
tracks.  I have read over several times and am still not sure of all of the 
caveats.  As Tom states below,  they are to be used mainly in "WRITE ONCE,  
READ MANY" environments.

-----Original Message-----
From: owner-freebsd-hardw...@freebsd.org 
[mailto:owner-freebsd-hardw...@freebsd.org] On Behalf Of Tom Evans
Sent: Tuesday, March 24, 2015 12:39 PM
To: Shehbaz Jaffer
Cc: FreeBSD FS; grarpamp; freebsd-hardware@freebsd.org
Subject: Re: Zoned Commands ZBC/ZAC, Shingled SMR drives, ZFS

On Tue, Mar 24, 2015 at 12:47 PM, Shehbaz Jaffer <shehbazjaffer...@gmail.com> 
wrote:
> Hi,
>
> I was wondering what cost advantage do SMR drive provide as compared 
> to normal CMR drive?
>
> 8TB SMR drive - $ 260
> 3TB CMR (Conventional Magnetic Recording drive) - $ 105
>

Purchase price is not irrelevant, but the key benefits are increased capacity 
per disk, and reduced power usage per disk and (multiplied by the increase in 
capacity) per TB. In other words, they disks consume less power, you need fewer 
of them, maybe allowing you to run fewer servers.

Of course, you also need a mainly read only workload. The RAID rebuild test 
from the linked review is *scary*. I wouldn't use these in ZFS raidz without 
plenty of disaster recovery testing - how long does it take to re-silver the 
pool when you lose a disk and what is the performance characteristics of the 
pool whilst it is doing so.

Cheers

Tom
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