On Tue, 2006-04-11 at 22:07 -0400, Guy wrote: > > } -----Original Message----- > } From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid- > } owner@xxxxxxxxxxxxxxx] On Behalf Of Ming Zhang > } Sent: Tuesday, April 11, 2006 6:13 PM > } To: Andy Smith > } Cc: linux-raid@xxxxxxxxxxxxxxx > } Subject: Re: mdadm + raid1 of 2 disks and now need to add more > } > } On Tue, 2006-04-11 at 20:32 +0000, Andy Smith wrote: > } > On Tue, Apr 11, 2006 at 07:25:58PM +0200, Laurent CARON wrote: > } > > Andy Smith wrote: > } > > >On Tue, Apr 11, 2006 at 04:41:30PM +0200, Shai wrote: > } > > >>I have two SCSI disks on raid1. > } > > >>Since I have lots of reads from that raid, I want to add two more > } > > >>disks to this raid so that read will be faster. > } > > >> > } > > >>How should I add the new disks? > } > > > > } > > >Is this possible with md currently: > } > > > > } > > >Create a RAID-10 on the two new disks specifying one disk missing > } > > >from each mirror. > } > > > > } > > >Then copy data over and add the two existing disks letting it > } > > >resync? > } > > > } > > Why not growing the array with 2 more disks? > } > > } > Well I guess a RAID-1 of 4 disks would be slightly more redundant > } > than a 4 disk RAID-10, but it would have half the capacity, and the > } > read performance would be very similar, no? > } > } raid1 of 4 will give u read performance like 1 disk; > } raid10 of 4 can give u read performance like aggregated 2 disks. > > I know RAID1 of 4 disks will give you read performance like 4 disks. > Unless your test or application is single threaded! Not likely I hope! > At least with the 2.4.31 kernel. for random read, u can make use of 4 disk in parallel. but for sequential workload, it has not much gain. > > A RAID1 of 4 disks will still function with any 3 failed disks. > Real good idea for remote systems. unless u data is that critical, u only get 25% disk utilization here. > > Also I think raid10 of 4 can give u read performance like 2 to 4 disks. > This depends more on the application. IMO. > You would have twice the space, but maybe not needed. > > > } > } > } > > } > } - > } To unsubscribe from this list: send the line "unsubscribe linux-raid" in > } the body of a message to majordomo@xxxxxxxxxxxxxxx > } More majordomo info at http://vger.kernel.org/majordomo-info.html > - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
