Hi there,
I was just clearing out a backlog of e-mail and noticed that nobody
commented on this post - it's out of my league but I was wondering if
anybody can shed any light on it...
Neal? Alvin?
Regards,
Corin
/------------------------+-------------------------------------\
| Corin Hartland-Swann | Tel: +44 (0) 20 7491 2000 |
| Commerce Internet Ltd | Fax: +44 (0) 20 7491 2010 |
| 22 Cavendish Buildings | Mobile: +44 (0) 79 5854 0027 |
| Gilbert Street | |
| Mayfair | Web: http://www.commerce.uk.net/ |
| London W1K 5HJ | E-Mail: [EMAIL PROTECTED] |
\------------------------+-------------------------------------/
On Tue, 20 Mar 2001, Richard Hirst wrote:
> I've just started playing with raid, so I may not have fully understood
> what is happening here, but..
>
> Look at raid1_error:
>
> static int raid1_error (mddev_t *mddev, kdev_t dev)
> {
> raid1_conf_t *conf = mddev_to_conf(mddev);
> struct mirror_info * mirrors = conf->mirrors;
> struct mirror_info *tmp;
> int disks = MD_SB_DISKS;
> int i;
>
> if (conf->working_disks == 1) {
> /*
> * Uh oh, we can do nothing if this is our last disk, but
> * first check if this is a queued request for a device
> * which has just failed.
> */
> for (i = 0; i < disks; i++) {
> if (mirrors[i].dev==dev && !mirrors[i].operational)
> return 0;
> }
> printk (LAST_DISK);
> } else {
> /*
> * Mark disk as unusable
> */
> for (i = 0; i < disks; i++) {
> if (mirrors[i].dev==dev && mirrors[i].operational) {
> mark_disk_bad(mddev, i);
> break;
> }
> }
> }
> return 0;
> }
>
> Now consider a two disk mirror where one disk is ok and the other has
> just been hotadded back in. That disk is marked 'spare' and
> 'operational' while it is being brought back in to sync.
>
> conf->working_disks is still 1, because it isn't updated until the sync
> is complete.
>
> Now we get an error on the new disk; the code does printk (LAST_DISK),
> which is harmless but wrong (the error was not on our last disk).
>
> Compare this with the case where you have a three disk mirror where two
> disks are ok and the third has just been hotadded back in.
> conf->working_disks is 2. An error on the new disk will take the
> 'else' path and end up calling mark_disk_bad(), which will decrement
> conf->working_disks to 1. Oops.
>
> Comments?
-
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to [EMAIL PROTECTED]
