From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Schinagl Subject: Re: Question about resync in RAID5 Date: Mon, 15 Apr 2013 22:27:20 +0200 Message-ID: <516C62A8.4050900@schinagl.nl> References: <1366106362-12886-1-git-send-email-sanbai@taobao.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <1366106362-12886-1-git-send-email-sanbai@taobao.com> Sender: linux-raid-owner@vger.kernel.org To: Robin Dong Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 16-04-13 11:59, Robin Dong wrote: > Dear Raid experts, > > I have a soft RAID5 volume and after one disk failed I replaced it wi= th > a new hard-disk. Then the raid5 volume begin to resync with WHOLE new > disk. > There is only 1G data in the RAID5 volume so I think resync whole dis= k > is not efficient. The md driver however does not know this. It syncs everything. Having said that, how do you know there's only 1 GB in use? Maybe there= =20 is a hidden partition for the remainder of the disk? Or, maybe it house= s=20 a encrypted container and in that container a nother encrpyted=20 countainer (check truecrypt on deniability). =46act is, you do not know how much data is or is not used, well not fo= r sure. > Take ZFS for example, when replacing with a new disk, it only resync = the > data which are written after the creation of the volume. but md is only the raid layer, zfs is the lower layer AND the=20 filesystem, you can't really fairly compare them. Btrfs may do this, bu= t=20 I don't know and don't think it's ready as replacement yet anyway. > > Is there any method to just resync WRITTEN data to new-added-disk ? O= r > any developing plan to add this feature? I highly doubt it, since, as said above, the md layer could not ever=20 possibly know what data is on the disk. > > ________________________________ > > This email (including any attachments) is confidential and may be leg= ally privileged. If you received this email in error, please delete it = immediately and do not copy it or use it for any purpose or disclose it= s contents to any other person. Thank you. > > =B1=BE=B5=E7=D3=CA(=B0=FC=C0=A8=C8=CE=BA=CE=B8=BD=BC=FE)=BF=C9=C4=DC=BA= =AC=D3=D0=BB=FA=C3=DC=D7=CA=C1=CF=B2=A2=CA=DC=B7=A8=C2=C9=B1=A3=BB=A4=A1= =A3=C8=E7=C4=FA=B2=BB=CA=C7=D5=FD=C8=B7=B5=C4=CA=D5=BC=FE=C8=CB=A3=AC=C7= =EB=C4=FA=C1=A2=BC=B4=C9=BE=B3=FD=B1=BE=D3=CA=BC=FE=A1=A3=C7=EB=B2=BB=D2= =AA=BD=AB=B1=BE=B5=E7=D3=CA=BD=F8=D0=D0=B8=B4=D6=C6=B2=A2=D3=C3=D7=F7=C8= =CE=BA=CE=C6=E4=CB=FB=D3=C3=CD=BE=A1=A2=BB=F2=CD=B8=C2=B6=B1=BE=D3=CA=BC= =FE=D6=AE=C4=DA=C8=DD=A1=A3=D0=BB=D0=BB=A1=A3 > -- > 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 http://vger.kernel.org/majordomo-info.html -- 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