From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roberto Spadim Subject: Re: SSD - TRIM command Date: Mon, 21 Feb 2011 16:43:08 -0300 Message-ID: References: <4D517F4F.4060003@gmail.com> <4D5245DF.4020401@hardwarefreak.com> <4D62ACFE.4020401@cfl.rr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: =?ISO-8859-1?Q?Mathias_Bur=E9n?= Cc: Phillip Susi , David Brown , linux-raid@vger.kernel.org List-Id: linux-raid.ids yeah, the idea of implement of TRIM at MD is to send TRIM to devices that was received by MD on filesystem level raid1 + no layout + all mirrors with TRIM support=3D> i think it=B4s ea= sy to implement... just send the command to mirros (ssd or hd, since they support it) for striped devices?! maybe could support, it=B4s more dificult for linear raid0 it could be easy too 2011/2/21 Mathias Bur=E9n : > On 21 February 2011 19:38, Mathias Bur=E9n = wrote: >> On 21 February 2011 19:32, Roberto Spadim wr= ote: >>> TRIM isn=B4t a problem, it=B4s a solution to optimize dynamic alloc= ation, >>> and life time of devices (SSD or harddisk) >>> i don=B4t see any problem to implement trim command on hard disks (= not >>> in linux, but at harddisk firmware level) >>> >>> hard disk have the same problem of ssd, allocation of badblocks, an= y >>> harddisk could implement trim and use it to realloc badblocks... >>> >>> -- >>> Roberto Spadim >>> Spadim Technology / SPAEmpresarial >>> >> >> I don't think you understand TRIM. It wouldn't work, and there is no >> need for it, on a HDD. AFAIK a HDD does not have the same penalty as= a >> SSD does when it needs to write to a (previously) used area. An SSD >> cannot do this without erasing the whole (block? page?), usually 512= KB >> in size (varies between different manufacturers), but the data that'= s >> on there still needs to be moved elsewhere first, block erased, data >> moved back the same time the new data is written together with it. >> AFAIK it works something like this anyway. The only benefit TRIM wil= l >> give you would be potentially faster writes, right. >> >> // M >> > > Plus support is needed from the kernel (done) filesystem (ext4 has > it). The filesystem seese the MD device, not the actual SSDs behind > it, so it would probably be quite complicated to implement passthroug= h > of the trim command in this case. > > // M > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid"= in > the body of a message to majordomo@vger.kernel.org > More majordomo info at =A0http://vger.kernel.org/majordomo-info.html > --=20 Roberto Spadim Spadim Technology / SPAEmpresarial -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html