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7

I found out the answer by asking on the mailing-list. btrfs doesn't do RAID per-volume, but rather on a per-chunk basis. The filesystem reserves "raw" space in (p.e.) 1GB chunks. Initializing the fs with raid1 means that everytime it tries to allocate a chunk, it tries to allocate a copy of this chunk on another device. This architecture allows mixed-size ...


6

Chunk size does not apply to raid1 because there is no striping; essentially the entire disk is one chunk. In short, you do not need to worry about the 4k physical sector size. Recent versions of mdadm use the information from the kernel to make sure that the start of data is aligned to a 4kb boundary. Just make sure you are using a 1.x metadata format.


4

Have a look at this question. I assume that is familiar to your problem. Recreating and even syncing a RAID-1 should not destroy data. Obviously the MD device starts at another offset now. Thus where mount looks for a superblock there is data. This can have happened in at least two ways: You (or rather: the default setting) have created the new array with ...


3

You can do that. You need to be a bit careful, but this is not dangerous¹ if you are very careful not to mistype anything and it doesn't leave any gotchas in the setup. I highly recommend not doing any of the manipulations on a live system. It's possible in some cases but requires extra care. Boot from a liveCD/liveUSB such as Parted or SystemRescueCD. ...


3

RAID is resyncing HDD There are 2 hints: "State : active, resyncing" "Rebuild status : 17% complete" It seems that your system is rebuilding your array (or it did not finished syncing it during installation). It should be bootable again once the array is finished rebuilding. For the time being, you could ty to boot in degraded mode at least. You can ...


3

You've mostly got them: slightly faster reads (but slower writes), and the ability to survive a failed drive without losing all the swapped-out processes. There's another: if your machine only has RAID-1 filesystems (or RAID-1 for the OS and RAID-5 for data, or similar arrangements), you might not want to complicate your setup further by having yet another ...


3

As already noted, there are a lot of options and which one is the best depends on your requirements. Since your systems is on RAID1, you can simply replace one disk and let your mirror rebuild itself. The removed disk can be used as a backup copy. In the past, for full system backups, I have used Ghost4Linux (aka G4L) and Mondo/Mindi. The former can save a ...


3

The native way of doing this is to create an LVM layer between your partitions and the disk. LVM has the capability to create snapshots which are basically instant point-in-time instances of the disk. The reason for this instead of just dd'ing the disk directly is that the contents of the disk may change while the dd is in progress. An LVM snapshot will not ...


3

We have configured all of our servers to run regular selftests with the following line in /etc/smartd.conf: # DEVICESCAN matches all hard disks found in /dev/ and applies the following # options to them. # # Default options from Debian: # -d removable don't exit when the device when a device vanishes # -n standby don't wake a device up that is ...


3

There's metadata at the start of the partition. If you do a mdadm -E /dev/sda1 you'll see where the data starts (Data Offset). That will be where your FS starts. You could use fdisk (for MBR-type partitioning) or gdisk (for GPT), to move the start of sda1 to the location of that Data Offset. For instance, if it says: Data Offset : 16384 sectors Run ...


3

An identical copy of your data is stored on each disk (provided the array is not "dirty"—e.g., if power is lost after writing to disk 0, but before writing to disk 1). However, the metadata is different; it allows mdadm & md to tell the two disks apart. Can you swap the cables around? You can swap the cables on the two disks. When you (or your distro's ...


3

You say you've spoken to Hetzner, who say it has software RAID. The problem is, it doesn't. Your cat /proc/mdstat says something like Personalities : [raid1] unused devices: <none> Which means no software RAID. If you had a broken software RAID, it would look something like Personalities : [raid1] md0 : active raid1 sdb1[1] (F) sda1[0] ...


2

OK—I'm not exactly sure what's going wrong on your box, but how about a quick summary of how this is supposed to work, to aid in troubleshooting. When you create an array with persistent superblocks (the quite sane default, and the way you've done it), mdadm stores various metadata on each disk. Included in that metadata is the array UUID, the array name, ...


2

I figured it out. First, I installed mdadm. sudo apt-get install mdadm Then I added an entry to /etc/mdadm/mdadm.conf (copied from the old system). Then I ran mdadm --assemble /dev/md0. Once that was done, lvdisplay showed my volume, and I could mount it with /etc/fstab.


2

There's nothing wrong with RAID 1 over three disks. Writing will be as fast as the slowest disk allows. All three disks will be utilized for reading, if you have enough processes doing reading. A single read operation is always served by a single disk only, so it depends on your application(s) whether it can make use of several disks worth of reading ...


2

THIS ENDED UP BEING A HARDWARE ISSUE Switching to the new shielded cables did not help, but replacing the old card with this one: http://www.amazon.com/gp/product/B000NTM9SY did get rid of the error messages and the strange behavior. Will post something new if anything changes. IMPORTANT NOTE FOR SATA ENCLOSURES: Even after doing the above, any drive ...


2

The disks are not 100% identical. Each linux softraid device contains a metadata block with a uniq guid. So dd might not work. The ports don't matter though. You can even put your drive into an extrernal usb box and it will still work. Doesn't work with hardware raid of course.


2

1) Why would all the rescheduled sectors be exactly 8 apart? Such gaps in the sector numbers are to be expected, the question is more how large those gaps would be (4k or larger). 8x 512 bytes are 4k which is the sector size most filesystems work with. So the filesystem probably requested to read 4k from the RAID, the RAID asks the /dev/sdb for that ...


2

I switched from long selftests to select,cont tests. It's like the long selftest, but only one slice of disk at a time. So while the long selftest may take well over a day (with an otherwise busy 3TB disk), the selective test can run every night when the server is the least busy and actually finish, without harming performance in the more busy hours. So ...


2

I usually use this simple check which is defined per drive and not globally per system (with DEVICESCAN option) - I'm interested in overall SMART health status and whether there are any pending sectors reallocation and any faulty sectors since last SMART test. Any suspicious events are mailed to my smart catch-all address then: /dev/sda -H -C 0 -U 0 -m ...


2

(Lev found the solution, I'm doing exegesis to explain why it works.) using its RAID controller to create a RAID1 array That's a bad sign: you're using fakeraid — a RAID implementation which is mostly implemented by the Windows driver with a little help from the firmware. You get all the downsides of hardware RAID (dependency on the firmware) with all ...


2

From what I understand you created 3 raid arrays, each with a mirror attached. You can mount each "half" of the pairs as normal disks but it's not advised while the array is running and both "halves" are active as that will desyncronize the copies and breaking the array. But in case of a failure they are there separately, and also if you use it for ...


1

Solved, to boot from second drive, in GRUB's command line: set root=(hd1) chainloader +1


1

That's a fakeraid managed with the dmraid package, which is why it shows up in /dev/mapper. I suggest backing up the system and blowing away the fake raid array with the bios utility. This may leave you with two identical disks, or may leave them both unusable ( hence, the backup ). Whether you have to restore or not, you can then add the second disk to ...


1

Something here doesn't make sense. A RAID1 array consists of 2 or more disks, all of which have the same contents. So if you make a 6-disk RAID1 array, you have five mirrors, not three. You may mean make three RAID1 arrays, each consisting of two disks. Then you'll have three different md devices to access. This won't hide the disks /dev/sd[a-f], but you ...


1

I got it working using the advice from here. Namely, I added /sbin/mdmon to the BINARIES array in mkinitcpio.conf. This looks a little like black magic to me, so a detailed answer with explanations is by all means welcome.


1

dd on the device is a way to clone a hard disk.



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