Guide to mirroring root / boot disks with solaris volume manager (disksuite) on solaris 10
Here's an step-by-step tutorial on mirroring your system drives with Solaris Volume Manager under Solaris 10. It will also work with solaris 8 and 9 (SVM was previously know as disksuite, Online Disk Suite, or just ODS. SVM is mature and stable - I'd recommend using it until ZFS matures.
Step 0:The following packages should be installed on Solaris 10: SUNWmdr (Solaris Volume Manager) SUNWmdu (Solaris Volume Manager) SUNWmdar (Solaris Volume Manager Assistant (Root) ) SUNWmdau (Solaris Volume Manager Assistant (Usr) ) You can use:
pkginfo -l | grep _packagename_to make sure these packages are installed. If not, you'll have to install them (from CD, or whatever - that's beyond the scope of this document.
Step 1: Partition disksI Suggest that you put a Sun Label on your disks. This may make them slightly smaller than they normally would be, but will allow you to use any replacement disk of the same general size if you need to replace a failed disk. IE: if you originally were using two Seagate ST336705LC drives and one failed, and you could only get a ST336704LC as a replacement, this wouldn't work - the ST336705LC by default has some extra blocks which makes it slightly larger that the ST336704LC. Partitions have to be the same size or larger or mirroring will fail. You can set this up by using
AVAILABLE DISK SELECTIONS: 0. c0t0d0NOTE: for the rest of this document, I will assume that your two system drives are c0t0d0 and c0t1d0.
/pci@1f,4000/scsi@3/sd@0,0 1. c0t1d0 /pci@1f,4000/scsi@3/sd@1,0 .. .. 10. c4t6d0 /pci@1f,4000/IntraServer-Ultra160,scsi@5/sd@6,0 Specify disk (enter its number): 10 selecting c4t6d0 [disk formatted] FORMAT MENU: disk - select a disk type - select (define) a disk type partition - select (define) a partition table current - describe the current disk format - format and analyze the disk repair - repair a defective sector label - write label to the disk analyze - surface analysis defect - defect list management backup - search for backup labels verify - read and display labels save - save new disk/partition definitions inquiry - show vendor, product and revision volname - set 8-character volume name ! - execute , then return quit format> type AVAILABLE DRIVE TYPES: 0. Auto configure 1. SUN146G 2. SUN18G 3. SUN36G ... 23. SEAGATE-ST318451LC-0003 24. SEAGATE-ST336704LC-0004 25. SEAGATE-ST318451LC-0002 26. other Specify disk type (enter its number): 2 selecting c4t6d0
Step 2: Partition the disks identicallyAgain, using format or whatever partitioning tool you prefer, partition the two system disks identically. Here's an example:
Part Tag Flag Cylinders Size Blocks 0 root wm 2701 - 7561 8.79GB (4861/0/0) 18432912 1 swap wu 0 - 2700 4.88GB (2701/0/0) 10242192 2 backup wm 0 - 18901 34.18GB (18902/0/0) 71676384 3 var wm 7562 - 9722 3.91GB (2161/0/0) 8194512 4 unassigned wm 9723 - 11870 3.88GB (2148/0/0) 8145216 5 unassigned wm 11871 - 16731 8.79GB (4861/0/0) 18432912 6 unassigned wm 16732 - 18892 3.91GB (2161/0/0) 8194512 7 unassigned wm 18893 - 18901 16.66MB (9/0/0) 34128I'll be using slice 0 (s0) for root (/), slice 3 (s3) for /var, and slice 1 (s1) for swap. Slice 7 will be used by disksuite for the metadb state database. You'll need root, /var, swap, and a small partition for the metadb at a minimum; I use the other partitions here for the excellent Solaris Live Upgrade feature.
OK, what's a metadb? From the metadb man page:
The metadevice state database contains the configuration of all metadevices and hot spare pools in the system. Additionally, the metadevice state database keeps track of the current state of metadevices and hot spare pools, and their components.
Step 3: create the metadb state databases
metadb -a -f -c 3 /dev/dsk/c0t0d0s7 metadb -a -c 3 /dev/dsk/c0t1d0s7You can view the current metadb configuration with:
Step 4: Create /etc/lvm/md.tab fileAt this point I create a text file called /etc/lvm/md.tab. From the man page:
The /etc/lvm/md.tab file contains Solaris Volume Manager configuration information that can be used to reconstruct your Solaris Volume Manager configuration.You could bypass this file and specify everything on the command line, but I find this easier, and it serves as documentation of what was done. Your file should look like this:
d10 -m d101 d102 1 d101 1 1 c0t0d0s0 d102 1 1 c0t1d0s0 d11 -m d111 d112 1 d111 1 1 c0t0d0s1 d112 1 1 c0t1d0s1 d12 -m d121 d122 1 d121 1 1 c0t0d0s3 d122 1 1 c0t1d0s3Thus the d10 metadevice is going to be our root (/) mirror, and d101 and d102 are going to be our root submirrors. Note that if you use metadevice names > d128, you might have to increase the "nmd" parameter is /kernel/drv/md.conf - see "Tips and Tricks" section, below.
Step 5: Set up one-way mirrorsAt this point, we can start creating our mirrors. Run the following commands to initialize the mirror devices, and half of the submirrors:
metainit d122 metainit -f d121 metainit d12 -m d121 metainit d102 metainit -f d101 metainit d10 -m d101 metaroot d10 metainit d112 metainit -f d111 metainit d11 -m d111
Step 6: Edit /etc/vfstabI suggest you make a quick backup of /etc/vfstab (IE: cp /etc/vfstab /etc/vfstab.ORIG). Then, change the entries for root (/), /var, and swap to reflect the new devices. IE:
/dev/dsk/c0t0d0s0 /dev/rdsk/c0t0d0s0 / ufs 1 no logging /dev/dsk/c0t0d0s3 /dev/rdsk/c0t1d0s3 /var ufs 1 no logging /dev/dsk/c0t0d0s1 - - swap - no -NEW:
/dev/md/dsk/d10 /dev/md/rdsk/d10 / ufs 1 no logging /dev/md/dsk/d12 /dev/md/rdsk/d12 /var ufs 1 no logging /dev/md/dsk/d11 - - swap - no -
Step 7: Reboot
sync sync init 6
Step 8: Sync the second half (submirror: make 2-way mirrors)
metattach d10 d102 metattach d11 d112 metattach d12 d122Note that the metattach command will come back almost immediately, but the disks will by syncing in the background. You can run the following command to see the progress of the sync, as well as to check for errors (denoted by "Maintenance" status):
metastatOR, to filter out the uninteresting output:
metastat | grep -i resyncAt this point, your system disks are mirrored. I would recommend setting up a small shell script to check for disk/mirroring problems (using metastat), and run it via cron.
Tips and Tricks:By default the system will not boot without one more than half the total metadb replicas. I suggest you put extra copies of the metadb on some of your non-system disks. If you only have two disks (IE: the system disks) I suggest you add this entry to your /etc/system file:
set md:mirrored_root_flag=1This will allow you to boot with only one metadb, if one of you disk drives fails.
Also, you might want to add:
set md_mirror:md_resync_bufsz = 2048to /etc/system as well. This greatly speeds up resyncs of failed mirror components by using 2 meg buffers instead of the default 128k. On one of our SunFire V215 machines, this increased the resync speed from 8-9 MB/second to 36-37 MB/second.
The default maximum number of devices is 128. IE: creating a metadevice named "d129" will fail with an error. You can increase this by changing:
nmd=400in /kernel/drv/md.conf. This required a "boot -r" to take effect.
Lastly, if your system ever has a panic or something causes it to reboot when one of the system disks is failed, you can manually boot from the other disk (without physically moving it) by running:
boot disk1from the OK prompt. Similarly:
boot disk0will boot off the primary disk (this is the default, and I wouldn't recommend changing it).