the mdadm.conf man page states:
The ARRAY lines identify actual arrays. The second word on the line may be
the name of the device where the array is normally assembled, [...].
Alternately the word <ignore> (complete with angle brackets) can be given in
which case any array which matches the rest of the line will never be
automatically assembled.
so let's say i have a raid that looks like:
/dev/md0:
Version : 1.2
Creation Time : Wed Oct 31 16:05:49 2012
Raid Level : raid6
Array Size : 1953522688 (1863.02 GiB 2000.41 GB)
Used Dev Size : 976761344 (931.51 GiB 1000.20 GB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Sun Nov 11 03:35:26 2012
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Name : vapier:0 (local to host vapier)
UUID : 51b812dc:094ea54b:f8f7b331:9982b16c
Events : 112048
Number Major Minor RaidDevice State
0 8 32 0 active sync /dev/sdc
1 8 0 1 active sync /dev/sda
4 8 16 2 active sync /dev/sdb
5 8 64 3 active sync /dev/sde
the man page says i should be able to prevent this from being auto-assembled
via `mdamd -As` by doing something like:
ARRAY <ignore> uuid=51b812dc:094ea54b:f8f7b331:9982b16c
or perhaps:
DEVICE /dev/sd[abce]
ARRAY <ignore> devices=/dev/sda,/dev/sdb,/dev/sde,/dev/sdc
unfortunately, this turns out to not be the case. mdadm goes ahead and auto-
assembles things anyways. looking at the code, it seems that it's due to the
code falling back if nothing was detected:
mdadm.c
...
do {
failures = 0;
successes = 0;
rv = 0;
for (a = array_list; a ; a = a->next) {
int r;
if (a->assembled)
continue;
if (a->devname &&
strcasecmp(a->devname, "<ignore>") == 0)
continue;
r = Assemble(ss, a->devname,
a, NULL, c);
if (r == 0) {
a->assembled = 1;
successes++;
} else
failures++;
rv |= r;
cnt++;
}
} while (failures && successes);
if (c->homehost && cnt == 0) {
/* Maybe we can auto-assemble something.
* Repeatedly call Assemble in auto-assemble mode
* until it fails
*/
int rv2;
int acnt;
ident->autof = c->autof;
do {
struct mddev_dev *devlist = conf_get_devs();
acnt = 0;
do {
rv2 = Assemble(ss, NULL,
ident,
devlist, c);
...
the idea is to be able to have a system with multiple raids (some of which are
dormant/backups), blacklist the ones that you want to keep idle, and bring
online all the rest.
-mike
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