Date: Sat, 25 May 2013 11:44:59 -0400 From: Paul Kraus <paul@kraus-haus.org> To: Michael Sierchio <kudzu@tenebras.com> Cc: saeedeh motlagh <saeedeh.motlagh@gmail.com>, freebsd-questions <freebsd-questions@freebsd.org> Subject: Re: file corruption solution (soft-update or ZFS) Message-ID: <9F319856-E79D-49F5-A0C9-3650DDC0C740@kraus-haus.org> In-Reply-To: <CAHu1Y704ufB_ie00hZrXw84WE5tT-b6t0O1uDjy69AbD7y9g-g@mail.gmail.com> References: <CAN%2BS=WC0ThjT6ox9YdUsAb6%2B%2Bf=%2BqfCLuct_tN=jsr3KYTezaw@mail.gmail.com> <alpine.BSF.2.00.1305230554360.98184@wonkity.com> <CAN%2BS=WDGdL5ZabOGp%2BrBshjmrd9so5Q=wMc5sfDGuEAZxLe3%2Bg@mail.gmail.com> <alpine.BSF.2.00.1305230629560.98184@wonkity.com> <CAHu1Y704ufB_ie00hZrXw84WE5tT-b6t0O1uDjy69AbD7y9g-g@mail.gmail.com>
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On May 23, 2013, at 11:09 AM, Michael Sierchio <kudzu@tenebras.com> = wrote: > On Thu, May 23, 2013 at 5:33 AM, Warren Block <wblock@wonkity.com> = wrote: >=20 >> .. >=20 >> One thing mentioned earlier is that ZFS wants lots of memory. 4G-8G >> minimum, some might say as much as the server will hold. >>=20 >>=20 > Not necessarily so - deduplication places great demands on memory, but = that > can be satisfied with dedicated cache devices (on SSD for performance = and > safety reasons). Without dedup, the requirements are more modest. The rule of thumb for DeDupe is 1GB physical RAM for every 1TB of = capacity. The issue is that the DeDupe metadata table must live in the = ARC for good performance. The discussion I have seen on the ZFS lists = indicates that L2ARC is not really adequate for this, so adding cache = devices (SSD's) don't really help. On the other hand, you can use ZFS without DeDupe with as little as 2GB = of total system RAM (depending on what else the system is doing). In my = experience, the amount of RAM depends on the amount of I/O not the = amount of storage. I find between 1GB and 3GB space for the ARC is = adequate. -- Paul Kraus Deputy Technical Director, LoneStarCon 3 Sound Coordinator, Schenectady Light Opera Company
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