/dev/md0:
Timing buffered disk reads: 1248 MB in 3.00 seconds = 415.65 MB/sec

mdadm - kernel - distro

1.12.0 - 2.6.15 - Ubuntu 6.06 LTS
2.5.6 - 2.6.20 - Ubuntu 7.04
2.6.3 - 2.6.24 - Ubuntu 8.04 LTS
2.6.7 - 2.6.27 - Ubuntu 8.10
2.6.7.1 - 2.6.28 - Ubuntu 9.04
1.12.0 - 2.6.9 - CentOS 4.5
2.5.4 - 2.6.18 - CentOS 5.0
2.5.6 - 2.6.18 - Debian 4.0r0
2.6.1 - 2.6.21 - Fedora 7

MDADM 2.x on kernels >2.6.17 supports online resizing of RAID 5 arrays

# cat /proc/mdstat

md0 : active raid5 sdf1[7] sdb1[0] sde1[5] sdg1[4] sdh1[3] sdd1[2] sdc1[1]
1465175424 blocks level 5, 64k chunk, algorithm 2 [7/6] [UUUUUU_]
[>....................] recovery = 1.3% (3331200/244195904) finish=2357.0min speed=1700K/sec

Ouch. Two files are used to control the speed of rebuilding RAID arrays in Linux.

/proc/sys/dev/raid/speed_limit_min
/proc/sys/dev/raid/speed_limit_max

Even though my _max file is set to 200,000K/sec and my system is not doing anything, my RAID 5 rebuild process is hovering around the _min rebuild speed, of 1,000K/sec. With my setup this will take approximately 40 hours to complete, which is too long for me to wait. So, I pushed the _min speed up to 10,000K/sec, which will now take 6 hours to finish, and use slightly more of my system’s idle resources.

root# echo “10000″ > /proc/sys/dev/raid/speed_limit_min

Later I set _min to 50,000K/sec, and the rebuild speed topped out at 25,000K/sec.

#cat /proc/mdstat

Personalities : [raid5]
md0 : active raid5 sdf1[7] sdb1[0] sde1[5] sdg1[4] sdh1[3] sdd1[2] sdc1[1]
1465175424 blocks level 5, 64k chunk, algorithm 2 [7/6] [UUUUUU_]
[=>...................] recovery = 5.1% (12661840/244195904) finish=149.9min speed=25726K/sec

The rebuild took less than 3 hours, down from the original 40.

$ cdrdao drive-info /dev/scd0

Cdrdao version 1.2.2 – (C) Andreas Mueller <andreas@daneb.de>
SCSI interface library – (C) Joerg Schilling
Paranoia DAE library – (C) Monty

Check http://cdrdao.sourceforge.net/drives.html#dt for current driver tables.

Using libscg version ‘ubuntu-0.8ubuntu1′

/dev/cdrw: LITE-ON DVDRW LH-20A1S Rev: 9L02
Using driver: Generic SCSI-3/MMC – Version 2.0 (options 0×0000)

Maximum reading speed: 8467 kB/s
Current reading speed: 8467 kB/s
Maximum writing speed: 8467 kB/s
Current writing speed: 8467 kB/s
BurnProof supported: yes
JustLink supported: no
JustSpeed supported: yes

Instructions here.

I plugged in a 250 GB Seagate 7200.10 hard drive into my Feisty box this evening, and to my surprise, /dev/sdd appeared along with a bunch of stuff in my dmesg output. This is on an NVIDIA Nforce 4 motherboard.

[189006.364000] ata3: exception Emask 0×10 SAct 0×0 SErr 0×150000 action 0×2 frozen
[189006.364000] ata3: hard resetting port
[189013.280000] ata3: SATA link up 1.5 Gbps (SStatus 113 SControl 300)
[189013.328000] ata3.00: ata_hpa_resize 1: sectors = 488397168, hpa_sectors = 488397168
[189013.328000] ata3.00: ATA-7: ST3250620AS, 3.AAJ, max UDMA/133
[189013.328000] ata3.00: 488397168 sectors, multi 0: LBA48 NCQ (depth 31/32)
[189013.392000] ata3.00: ata_hpa_resize 1: sectors = 488397168, hpa_sectors = 488397168
[189013.392000] ata3.00: configured for UDMA/133
[189013.392000] ata3: EH pending after completion, repeating EH (cnt=4)
[189013.392000] ata3: EH complete
[189013.396000] scsi 2:0:0:0: Direct-Access     ATA      ST3250620AS      3.AA PQ: 0 ANSI: 5
[189013.396000] ata3: bounce limit 0xFFFFFFFFFFFFFFFF, segment boundary 0xFFFFFFFF, hw segs 61
[189013.400000] SCSI device sdd: 488397168 512-byte hdwr sectors (250059 MB)
[189013.404000] sdd: Write Protect is off
[189013.404000] sdd: Mode Sense: 00 3a 00 00
[189013.408000] SCSI device sdd: write cache: enabled, read cache: enabled, doesn’t support DPO or FUA
[189013.412000] SCSI device sdd: 488397168 512-byte hdwr sectors (250059 MB)
[189013.412000] sdd: Write Protect is off
[189013.412000] sdd: Mode Sense: 00 3a 00 00
[189013.416000] SCSI device sdd: write cache: enabled, read cache: enabled, doesn’t support DPO or FUA
[189013.416000]  sdd: unknown partition table
[189013.432000] sd 2:0:0:0: Attached scsi disk sdd
[189013.432000] sd 2:0:0:0: Attached scsi generic sg4 type 0

Download all the Ubuntu i386 and AMD64 ISOs with one command.

wget ftp://mirrors.kernel.org/ubuntu-releases/7.04/ubuntu-7.04-{desktop,server,alternate}-{i386,amd64}.iso

Maybe I like it because it’s in my price range (unlike that 108″ LCD they keep showing off), but the new Antec Sonata III (pic) case looks like a stealth fighter compared to my aging Sonata I. I’ve grown tired of my current case, but it is quiet. This may get me to upgrade. Or I’ll go with the Antec Nine Hundred.

Sweet.

I recently upgrade my main workstation’s hard drive under Ubuntu 6.10 and noticed a couple things changed during the process. Here are my instructions for a fast and reliably hard drive swap. I’m using SATA drives without LVM using the default Ubuntu install and partition options for this howto.

1. Prepare
1. Shutdown your machine and install your new hard drive. Don’t mess with your current hard drive (yet)
2. Find a LiveCD, I used the Ubuntu 6.10 LiveCD, it matched my OS, but it doesn’t have to. Knoppix should work fine.
3. Boot using your LiveCD
4. After booting, open a terminal and “sudo su” to become root
2. Setup your new drive
1. Use cfdisk /dev/sda to look at your partitions on your current drive. I have sda1 of type linux as most of my current drive, and a 6 GB sda5 as linux swap at the end
2. Duplicate this on your new drive using cfdisk /dev/sdb, adjusting for space as necessary. I created a new primary partition using cfdisk using all but 6 GB of space, then a new logical partition using the rest of the space. You must create the partitions in this order to get the right numbering
3. make the primary partition to bootable
4. set the swap partition as type 82 (linux swap)
5. save and quit
6. create filesystems on the new partitions using mkfs.ext3 /dev/sdb1 and mkswap /dev/sdb5
3. Copy data
1. Make directories to mount your old and new partitions, in this case, /mnt/sda1 and /mnt/sdb1
2. Mount your drives to these partitions using mount /dev/sda1 /mnt/sda1 and mount /dev/sdb1 /mnt/sdb1
3. Copy all your data from your old drive to your new drive using cp -a /mnt/sda1/* /mnt/sdb1/ . The -a will preserve owners, permissions, date, etc.
4. Get up and do something else. It took 70 minutes for my machine to copy about 150 GB of data from one drive to the other
4. Fix the boot options
1. This is where Ubuntu 6.10 differs from previous versions. Fstab and menu.lst both use UUID numbers to find partitions. To get the UUID number of your new partitions, run vol_id /dev/sdb1 and vol_id /dev/sdb5 . Copy these numbers into their appropriate places in your /mnt/sdb1/etc/fstab and /mnt/sdb1/boot/grub/menu.lst files. You may need to dig around the menu.lst to find all the entries.
2. Now install grub onto the MBR of the new drive to make it bootable. To do this I first chroot into my new system using chroot /mnt/sdb1 /bin/bash . Now that you’re in the new system, run grub. Inside grub, run setup (hd1,0) then root (hd1) . This will differ if you have a different drive setup. Quit grub (quit).
5. Finish up
1. Logout of your chroot (logout), unmount your mounted drives umount /dev/sda1 and umount /dev/sdb1, and shutdown your computer. Disconnect your old drive, plug your new drive into the old drive’s cable, and start your computer back up. If everything went well, it will boot back up as if nothing happened.