[pve-devel] [PATCH pve-doc 2/5] ZFS RAM usage more precise.

[Alexandre DERUMIER]

>>Who as an 1TB l2arc?
In past, I try that ;)  (30TB storage with 1TB l2arc).

>>and yes if you enable Dedub you need additional 320Bytes per Block.
>>This is only an approximately Ram usage where user can calculate.

yes, I just wonder if it could be interesting to warn user about that in doc.
(Anyway, I think proxmox use 128k block, so it should not use too much memory)

----- Mail original -----
De: "Wolfgang Link" <w.link at proxmox.com>
À: "pve-devel" <pve-devel at pve.proxmox.com>
Envoyé: Mardi 4 Octobre 2016 09:07:13
Objet: Re: [pve-devel] [PATCH pve-doc 2/5] ZFS RAM usage more precise.

Who as an 1TB l2arc? 
and yes if you enable Dedub you need additional 320Bytes per Block. 
This is only an approximately Ram usage where user can calculate. 

On 10/04/2016 08:51 AM, Alexandre DERUMIER wrote: 
>>> +ZFS uses a lot of memory, a good calculation is 4GB plus 1GB RAM 
>>> +for each TB RAW disk space if you want to use ZFS. 
> 
> also, if l2arc is enabled, zfs take 240 bytes memory for each block in l2arc. 
> if you use small block (4k) for your pool for example, this can be very huge (64GB memory for 1TB) 
> 
> 
> 
> ----- Mail original ----- 
> De: "Wolfgang Link" <w.link at proxmox.com> 
> À: "pve-devel" <pve-devel at pve.proxmox.com> 
> Envoyé: Lundi 3 Octobre 2016 09:28:56 
> Objet: [pve-devel] [PATCH pve-doc 2/5] ZFS RAM usage more precise. 
> 
> --- 
> pve-installation.adoc | 4 ++-- 
> 1 file changed, 2 insertions(+), 2 deletions(-) 
> 
> diff --git a/pve-installation.adoc b/pve-installation.adoc 
> index 032fd51..485f077 100644 
> --- a/pve-installation.adoc 
> +++ b/pve-installation.adoc 
> @@ -135,8 +135,8 @@ required for lvmthin snapshots). 
> ZFS Performance Tips 
> ^^^^^^^^^^^^^^^^^^^^ 
> 
> -ZFS uses a lot of memory, so it is best to add additional 8-16GB RAM 
> -if you want to use ZFS. 
> +ZFS uses a lot of memory, a good calculation is 4GB plus 1GB RAM 
> +for each TB RAW disk space if you want to use ZFS. 
> 
> ZFS also provides the feature to use a fast SSD drive as write cache. The 
> write cache is called the ZFS Intent Log (ZIL). You can add that after 
> 

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