Date: Thu, 12 Nov 2009 18:24:01 -0800 From: Artem Belevich <fbsdlist@src.cx> To: "Sam Fourman Jr." <sfourman@gmail.com> Cc: Rick Macklem <rmacklem@uoguelph.ca>, Dan Nelson <dnelson@allantgroup.com>, Ivan Voras <ivoras@freebsd.org>, freebsd-current@freebsd.org, Scott Ullrich <sullrich@gmail.com> Subject: Re: Help ZFS FreeBSD 8.0 RC2 Write performance issue Message-ID: <ed91d4a80911121824u7d690dd5o4721a1026cc02597@mail.gmail.com> In-Reply-To: <11167f520911121813v29441ac4v2e3dfa6f4386ba4e@mail.gmail.com> References: <11167f520911111050j36dd94far667c81e6f5c18e69@mail.gmail.com> <Pine.GSO.4.63.0911121147310.9126@muncher.cs.uoguelph.ca> <11167f520911121044l74744c30u5a4d9ca008ab863c@mail.gmail.com> <d5992baf0911121048o76c1543el2b4d9de84ffb107@mail.gmail.com> <11167f520911121101o403751ddmb544dfaf1c61bf1e@mail.gmail.com> <ed91d4a80911121219sa0f3fa3s934791725028a966@mail.gmail.com> <d5992baf0911121314k7f535f2cra2d3e8367774d8ca@mail.gmail.com> <11167f520911121339y4161a1a2sae8b6196c3b7a1fb@mail.gmail.com> <d5992baf0911121643r13a6e87bx33efa0a3ec4ef463@mail.gmail.com> <11167f520911121813v29441ac4v2e3dfa6f4386ba4e@mail.gmail.com>
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On Thu, Nov 12, 2009 at 6:13 PM, Sam Fourman Jr. <sfourman@gmail.com> wrote: > so you are suggesting that it is possible that 2x SSD disks would get > me the other 60MB/sec I guess you can test what SSDs would buy you in terms of performance. Disable ZIL and run your performance test. If ZIL is what's causing issues, then you will see a speedup. In this case proper log on SSDs should bring your performance fairly close to those numbers, provided SSDs can handle your write rate. If disabling ZIL does not help much, then separate log device will not help much either. On a side note, log device does not have to be big. According to Sun you'll need ~1/2 of your physical memory size: http://docs.sun.com/app/docs/doc/819-5461/gfgaa?a=view Given that typical SSDs these days are quite a bit larger than your typical RAM size, you may use the rest of the SSD as L2ARC. --Artem
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