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Message from discussion Seagate 3TB ST3000DM001 as raidz with or whithout ashift
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Gordan Bobic  
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 More options May 28 2012, 3:14 pm
From: Gordan Bobic <gordan.bo...@gmail.com>
Date: Mon, 28 May 2012 20:14:57 +0100
Local: Mon, May 28 2012 3:14 pm
Subject: Re: [zfs-discuss] Seagate 3TB ST3000DM001 as raidz with or whithout ashift
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On 28/05/2012 15:49, Aneurin Price wrote:

> On 26 May 2012 13:31, Ivailo Karamanolev<ivail...@gmail.com>  wrote:
>> Performance will be affected, I am using these drives with ashift 12 and I
>> am very happy with the performance, but have no benchmark data. Resilience
>> and data safety are basically not affected.

> Seagate do *claim* that their SmartAlign technology allows their 4k
> disks to be used as a drop-in replacement for 512b disks without
> performance degradation, but I don't know how well it works in
> practice. I would be interested in trying to benchmark this though
> since I have a pool that's a couple of years old and creating a new
> pool to transfer everything into would mean spending a fortune on new
> disks all at once.

My guess would be that the disk understands how to read the partition
table when you write it and adjusts the old-style 63-sector alignment to
+1 to iron it out.

I wouldn't bank on it doing it right every time, though.

> I'm likely to buy one or two of those in the coming months - does
> anyone have any suggestions on how to test this? I imagine I could
> create a new single-disk pool and benchmark it, then repeat with a
> different ashift value, but what tests would be relevant?

4KB random read/write test using iozone should be reasonably telling.

Gordan


 
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