From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phillip Susi Subject: Re: SSD - TRIM command Date: Mon, 21 Feb 2011 21:38:07 -0500 Message-ID: <4D63218F.2000309@cfl.rr.com> References: <4D62CF5F.6080007@cfl.rr.com> <20110222003610.GB29101@bounceswoosh.org> 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: Roberto Spadim Cc: =?ISO-8859-1?Q?Mathias_Bur=E9n?= , "Eric D. Mudama" , David Brown , linux-raid@vger.kernel.org List-Id: linux-raid.ids On 02/21/2011 08:55 PM, Roberto Spadim wrote: > it can be used for badblock reallocation if harddisk have it > a harddisk is near to NOR ssd with variable accesstime, if head is > near sector to be read/write accesstime is small, if sector is far > from head, access time increase (normaly<=1 disk revolution if head > control system is good, for 7200rpm 1revolution is near to 8.33ms) Bad blocks are only reallocated when you write to them. Since they are bad, you can't read the previous contents anyway, so it does not matter whether the OS cared about it before or not. You seem to not understand the fundamental purpose of TRIM. Hard disks only reallocate blocks when they go bad. SSDs move blocks around all the time. That process can be optimized if the drive knows that the OS does not care about certain blocks. Hard drives don't do this, so they have no reason to support TRIM.