> -----Original Message----- > From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid- > owner@xxxxxxxxxxxxxxx] On Behalf Of maarten van den Berg > Sent: Thursday, May 27, 2004 4:20 PM > To: linux-raid@xxxxxxxxxxxxxxx > Subject: Re: Moving a RAID5 array > > On Friday 28 May 2004 00:04, Tim Harvey wrote: > > Disclaimer: I'm not a real expert, but have had my share of raid5 > experiences. > > > My question is that, not being very familiar with Linux raid or mdadm, > > I'm wondering if I can mount the array on my Linux system when the > > devices are other than described above (they would likely be /dev/hdc1, > > /dev/hdd1, etc as my boot/root drives use hda/hdb). Additionally, how > > I did shuffle my disks at several points in time, and it figures that out > by > itself somehow (there must be something in the superblock identifying > which > drive it is). > > > should I go about mounting this array in a way that if anything doesn't > > work right, it doesn't trash the array. I'm a little paranoid that I > > may do something wrong and the raidutils will start reconstructing or > > otherwise altering the information on the array. > > There are several things to note. You want to disallow the raid to start > any > reconstruction, and you need to skip any fsck at mount, as well as > replaying > of journals if they are journaling filesystems. It looks like I need to do an 'mdadm --assemble' to assemble the previously created array into an active array. But I'm not clear how to examine the /dev/md0 device to see what partitions are available (fdisk didn't work in a test... I guess its not compatible with /dev/md0). > > Issue #1 Can be assured (AFAIK) by just attaching one disk less. Then the > array will be in degraded mode and cannot / will not attempt a resync. > In addition, this will enable you to choose another set of disks, should > the > outlook on the first three be less than favourable... > Does disallowing the raid to start any reconstruction mean that the array is not 'started' and that I cannot mount the filesystem? I guess I'm not clear if there is a difference between the array being 'started' and 'allowing reconstruction'. Is leaving a disk out of the RAID5 array the only way to force this to occur? I noticed mdadm has a --readonly option but I'm not sure if it affects the assemble mode. > Issue #2 Should be assured by mounting read-only, without prior fsck. > Sounds like a safe bet to mount the partition read-only. How can I examine /dev/md0 to see what partitions are available? I'm fairly certain XFS is used. The RAID HOWTO doesn't seem to go into detail regarding how to examine filesystems on an array. > Issue #3 I'm not sure about. Consult the manualpage detailing your > specific > filesystem... Maybe instead of mounting you could run an fsck with an > option > to do only a test-run / dry-run i.e. allow no writes whatsoever during > fsck. > If that fsck succeeds, chances are very good that all is in order. Is this to ensure no writing occurs in case something didn't work correctly? If everything looks ok in a dry-run I'll want to mount and allow fsck and journaling to complete I assume. Again, can the --readonly option be used to keep the device from being written at the device level for a dry-run? > > Anyway, my guess is, you'll have no trouble at all. A power-loss is not > the > very worst that can happen to an array. In my humble opinion... > > > Thanks for any help. I've read over the Linux RAID FAQ and looked > > through the man pages for mdadm, but I'm pretty paranoid about loosing > > the data and want to consult the experts here. > > <Grin> No backups huh ? Been there, done that, still got my data back. > :) I guess I've been educated :) Ironically the power outages occurred due to my own blunders while hooking up a 2nd device to use as a backup. Thanks for your help! Tim > > Well, good luck with your endeavors ! > > Maarten > > > - > > 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 > > -- > When I answered where I wanted to go today, they just hung up -- Unknown > > - > 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 - 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
