[OmniOS-discuss] Moving a zfs pool from server to another with less memory.

[Jim Klimov]

On 2013-10-30 16:44, Svavar Örn Eysteinsson wrote:
>
> Hi.
>
> Are there any special configuration or setup that I need to take consider ?
>
> I'm currently moving a 14TB ZFS pool from a out-dated OpenIndiana server with 16GB in RAM.
> The new server will only provide 8GB of RAM, and will be running OmniOS.
> The new server has a maximum of 8GB of RAM, so there is no option extending the RAM.
>
> I have also in plans to extend the size of the pool to at least 20TB.
> It only serves as a archive server. not much of client activity, only rsync and archival stuff.

First of all, probably, make sure that your RAM is ECC (my "limited"
NAS at home was based on desktop hardware which only used non-ECC
memory which could be the cause of some of my problems - with no
good way to check). Also, this amount of memory is very small for
dedup for example.

Otherwise, especially for an archival system with little random IO
(sans scrubbing) it might not matter much... Basically, this all
revolves around the "working set" (or "hot data") size, so that for
the data you mostly use your data or metadata is speedily available
in RAM. There are rough estimates like "you need 1GB RAM per TB of
storage", but exact numbers depend on the system's usage and data
layout (i.e. average number of blocks per TB).

HTH,
//Jim