> -----Original Message----- > From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid- > owner@xxxxxxxxxxxxxxx] On Behalf Of David Brown > Sent: Thursday, May 05, 2011 2:27 AM > To: linux-raid@xxxxxxxxxxxxxxx > Subject: Re: mdadm raid1 read performance > > On 05/05/2011 02:40, Liam Kurmos wrote: > > Cheers Roberto, > > > > I've got the gist of the far layout from looking at wikipedia. There > > is some clever stuff going on that i had never considered. > > i'm going for f2 for my system drive. > > > > Liam > > > > For general use, raid10,f2 is often the best choice. The only > disadvantage is if you have applications that make a lot of synchronised > writes, as writes take longer (everything must be written twice, and > because the data is spread out there is more head movement). For most > writes this doesn't matter - the OS caches the writes, and the app > continues on its way, so the writes are done when the disks are not > otherwise used. But if you have synchronous writes, so that the app > will wait for the write to complete, it will be slower (compared to > raid10,n2 or raid10,o2). > > The other problem with raid10 layout is booting - bootloaders don't much > like it. The very latest version of grub, IIRC, can boot from raid10 - > but it can be awkward. There are lots of how-tos around the web for > booting when you have raid, but by far the easiest is to divide your > disks into partitions: > > sdX1 = 1GB > sdX2 = xGB > sdX3 = yGB > > Put all your sdX1 partitions together as raid1 with metadata layout > 0.90, format as ext3 and use it as /boot. Any bootloader will work fine > with that (don't forget to install grub on each disk's MBR). > > Put your sdX2 partitions together as raid10,f2 for swap. > > Put the sdX3 partitions together as raid10,f2 for everything else. The > most flexible choice is to use LVM here and make logical partitions for > /, /home, /usr, etc. But you can also partition up the md device in > distinct fixed partitions for /, /home, etc. if you want. I agree, except that I like to have separate physical devices for booting and raw disks for the data. My servers each have a pair of 500G hard drives partitioned into three sections. First, /dev/sdX1 is a small partition which contains only /boot, it is read-only, and can be mounted at boot time, or not. As you say, it has a 0.90 superblock, although I chose an ext2 file system. Next, /dev/sdX2 uses about half the disk and is mounted at /. Finally, I use the rest of the disk, /dev/sdX3, as swap space. I chose all three to be RAID1. The data drives are all >= 1Tb, unpartitioned, and assembled into RAID6 arrays of 10 or more members, each. These systems use so little swap space and so rarely, I'm not sure I see any benefit to RAID10,f2 for them. Is there? -- 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
