From nobody Mon Mar 04 14:17:09 2024 X-Original-To: freebsd-questions@mlmmj.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mlmmj.nyi.freebsd.org (Postfix) with ESMTP id 4TpLP466Ngz5Cgs9 for ; Mon, 4 Mar 2024 14:17:12 +0000 (UTC) (envelope-from feenberg@nber.org) Received: from mail2.nber.org (mail2.nber.org [198.71.6.79]) by mx1.freebsd.org (Postfix) with ESMTP id 4TpLP443xZz58b7 for ; Mon, 4 Mar 2024 14:17:12 +0000 (UTC) (envelope-from feenberg@nber.org) Authentication-Results: mx1.freebsd.org; none Received: from sas1.nber.org (sas1.nber.org [198.71.6.89]) by mail2.nber.org (8.17.2/8.16.1) with ESMTPS id 424EH9b9072547 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NOT); Mon, 4 Mar 2024 09:17:10 -0500 (EST) (envelope-from feenberg@nber.org) Date: Mon, 4 Mar 2024 09:17:09 -0500 (EST) From: Daniel Feenberg To: Andrea Venturoli cc: freebsd-questions@freebsd.org Subject: Re: ZFS ARC memory requirements In-Reply-To: <7f7a9f1f-8a2b-41ef-a6a7-1dc1e2f160af@netfence.it> Message-ID: <83a5e3e2-a211-c524-1c8f-700802d148f@nber.org> References: <7f7a9f1f-8a2b-41ef-a6a7-1dc1e2f160af@netfence.it> List-Id: User questions List-Archive: https://lists.freebsd.org/archives/freebsd-questions List-Help: List-Post: List-Subscribe: List-Unsubscribe: Sender: owner-freebsd-questions@freebsd.org X-BeenThere: freebsd-questions@freebsd.org MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed X-KLMS-Rule-ID: 1 X-KLMS-Message-Action: clean X-KLMS-AntiSpam-Status: not scanned, disabled by settings X-KLMS-AntiSpam-Interceptor-Info: not scanned X-KLMS-AntiPhishing: Clean, bases: 2024/03/04 13:23:00 X-KLMS-AntiVirus: Kaspersky Security for Linux Mail Server, version 8.0.3.30, bases: 2024/03/04 08:11:00 #23960386 X-KLMS-AntiVirus-Status: Clean, skipped X-Spamd-Bar: ---- X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spamd-Result: default: False [-4.00 / 15.00]; REPLY(-4.00)[]; ASN(0.00)[asn:26287, ipnet:198.71.6.0/23, country:US] X-Rspamd-Queue-Id: 4TpLP443xZz58b7 On Mon, 4 Mar 2024, Andrea Venturoli wrote: > > I read the rule of thumbs for RAM is 1GB per TB of storage, which would > possibly mean 192GiB!!!, but I also read this is argued upon. We have a number of large ZFS stores used for both production and backup. Most have 64GB and that seems more than enough. We use compression, but do not do de-duplication. I believe the advice you have read accounts for de-duplication, which is memory-intensive. Daniel Feenberg