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Date:      Fri, 3 Jun 2022 16:05:23 -0600 (MDT)
From:      Dale Scott <dalescott@shaw.ca>
To:        David Christensen <dpchrist@holgerdanske.com>
Cc:        questions <questions@freebsd.org>
Subject:   Re: Effect of using SATA 2.x and 3.x in zfs mirrored config
Message-ID:  <1282680065.59022622.1654293923886.JavaMail.zimbra@shaw.ca>
In-Reply-To: <8dcf342c-74f6-242d-338b-1c8cd2dee54f@holgerdanske.com>
References:  <1706301853.51806224.1654176891423.JavaMail.zimbra@shaw.ca> <8dcf342c-74f6-242d-338b-1c8cd2dee54f@holgerdanske.com>

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----- Original Message -----
> From: "David Christensen" <dpchrist@holgerdanske.com>
> To: "questions" <questions@freebsd.org>
> Sent: Thursday, June 2, 2022 2:14:52 PM
> Subject: Re: Effect of using SATA 2.x and 3.x in zfs mirrored config

> On 6/2/22 06:34, Dale Scott wrote:
>> Hi all, I installed FreeBSD "root-on-zfs" using the installer on two new WD Blue
>> 1TB SSDs (mirrored).
>> 
>> Looking in dmesg, I see one of the drives is using SATA 3 (600MB/s transfer),
>> and the other is using SATA 2 (300MB/s transfer). Will mixing SATA 2 and SATA 3
>> drives cause any technical issues? Is there any reason why I should use SATA 2
>> for both drives?
>> 
> I do not know if the SATA 3 Gbps vs. 6 Gbps mismatch will break ZFS.
> 
> If the computer boots and runs, I would hammer it with filesystem
> benchmarks.  dbench(1) comes to mind.
> 
> It appears that computer has PCIe 1.0 (2.5 Gbps per channel):
> 
> https://support.hp.com/us-en/document/c02779499
> 
> Perhaps a PCIe x4 to SATA 6 Gbps HBA that is backwards compatible with
> PCIe 1.0 could run a single SATA 6 Gbps SSD at full speed (?).  You
> could ask around with various manufacturers' technical support, or just
> buy a card and find out:
> 
> https://docs.broadcom.com/doc/12353332
> 
> David

Thanks David for PCIe HBA suggestion. I like the idea of running benchmarks, but I'm lery of using up all the drives writes just to confirm all is ok (and the server has been in use for about 5 months now without issue albeit under relatively light disk load).


--- 
Dale Scott 
www.dalescott.net 
https://ca.linkedin.com/in/dalescott




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