From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lutz Vieweg Subject: Re: Software RAID and TRIM Date: Wed, 20 Jul 2011 14:20:08 +0200 Message-ID: References: <4E235984.2070704@5t9.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 07/20/2011 09:42 AM, David Brown wrote: >> http://tdm27.wordpress.com/2011/07/19/some-solid-state-drive-benchmarks/ > > The telling figure here, though, is that TRIM made the single drive significantly slower. More precisely, online-TRIM of ext4 on Intel SSDs seems to be a bad combination. I think it's clear you cannot gain much from TRIM if you're willing to spend the money for 2 times overprovisioning, anyway. You can lose significantly from online-trim when the filesystem issues a lot of TRIM commands all the time and when the SSD is slow to process them. TRIM gains you an advantage with less over-provisioning, and is better done in batches after significant amounts of data have been written/deleted. When you try with different levels of over-provisioning, also try with batched discards (fstrim) between runs of your benchmark. Regards, Lutz Vieweg