[OmniOS-discuss] Moving The Root Pool

[Jim Klimov]

14 февраля 2017 г. 15:06:37 CET, Andre Kruger <andre at ak47.co.za> пишет:
>
>
>On 2017/02/14 15:38, Stephan Budach wrote:
>> Hi Andre,
>>
>> well, I wouldn't call it dead… there is a way to accomplish, what you
>
>> want and I had already performed such an action before. However, I 
>> cannot recall all the steps necessary. Looking at the link Dan 
>> provided, the steps lined out in the document  are still valid and I 
>> don't think that there is an easier way to do it.
>>
>> Regarding the other issues about a general advice against using a SSD
>
>> as a rpool… there is none I know of. Depending on the manufacturer
>you 
>> may want to provide enough free space on the SSD, as I don't know if 
>> Ilumos/OmniOS have come up to speed regarding TRIM, but you can
>always 
>> counter that by providing enough space for the SSD's GC.
>> If a SSD is suited as a rpool in Ilumos may be hard to judge. All I 
>> know is, that you should stay away from Samsung EVOs… unless you're 
>> operating them in a Windows environment.
>>
>> Cheers,
>> Stephan
>
>Hi Stephan
>
>No sorry I think there is a misunderstanding. SSDs are excellent for 
>rpool. I was talking about taking a HDD on which rpool is installed ie
>a 
>running system. Shutting it down. Then cloning the HDD to the SSD. Plug
>
>the SSD into the previously running machine and just boot it up. Using 
>this method is much easier, simpler, and faster.
>
>But, on many Windows forums there are warning cloning a HDD directly to
>
>an SSD, of the boot drive drive C, and then using the SSD. Apparently 
>many users have experienced very slow performance. You can however
>clone 
>from HDD to HDD or SSD to SSD without these performance problems. From 
>there my question if anybody knows of a caveat not to do it in this way
>
>if I want to clone my rpool from HDD to SSD. If none I would rather
>walk 
>this path as it is far less trouble.
>
>BTW, why should one steer clear of the Samsung EVO's?
>
>
>Regards
>André

My take on it is that cloning may fail you because of native sector size that might be 512b to 4k on HDDs but may be 4k or 8k on SSDs. Using old block sizes may be suboptimal (RMW cycles) or impossible (if storage firmware does not virtualize legacy sector sizes).

So you'd be better off creating a pool on the ssd 'natively' and zfs send'ing the datasets from HDD recursively.

Jim
--
Typos courtesy of K-9 Mail on my Samsung Android