Tag Info

Hot answers tagged

21

You should not mount it directly using mount. You need first to run mdadm to assemble the raid array. A command like this should do it: $ mdadm --assemble --run /dev/md0 /dev/sdc1 If it refuses to run the array because it will be degraded, then you can use --force option. This is assuming you don't have /dev/md0 device. Otherwise, you need to change this ...


20

RAID-5 is a fault-tolerance solution, not a data-integrity solution. Remember that RAID stands for Redundant Array of Inexpensive Disks. Disks are the atomic unit of redundancy -- RAID doesn't really care about data. You buy solutions that employ filesystems like WAFL or ZFS to address data redundancy and integrity. The RAID controller (hardware or ...


18

What you have is evidently not hardware RAID but software RAID with a BIOS interface, often called fakeRAID. The main job of putting the disks in an array is done by the Windows driver. Related reading: How do I differentiate “fake RAID” from real RAID? There are two advantages to hardware RAID over software RAID: it's independent of the operating system ...


16

Generally I'd say RAID 1+0 will tend to be more widely used than 1+5 or 1+6 because RAID 1+0 is reliable enough and provides marginally better performance and more usable storage. I think most people would take the failure of a full RAID 1 pair within the RAID 1+0 group as a pretty incredibly rare event that's worth breaking out the backups for - and ...


16

It's a waste of time. You won't be able to induce failure or stress the drives in a meaningful manner. You have RAID, and that's a good start. Just make sure you have monitoring in place to actually detect failures as they occur and backups to protect against disaster.


14

The practical answer lies somewhere at the intersection of hardware RAID controller specifications, average disk sizes, drive form-factors and server design. Most hardware RAID controllers are limited in the RAID levels they support. Here are the RAID options for an HP ProLiant Smart Array controller: [raid=0|1|1adm|1+0|1+0adm|5|50|6|60] note: the "adm" ...


13

You're most likely talking about this http://www.debian-administration.org/articles/238 "Now use mdadm to create the raid arrays. We mark the first drive (sda) as "missing" so it doesn't wipe out our existing data..."


12

S.M.A.R.T. can be used as an indicator that there are drive problems but can never be relied upon to indicate that a drive is good. When there is disagreement between multiple diagnostic systems always favour the one that shows the worst results.


11

You have diminishing returns on reliability. RAID 6 is pretty unlikely to compound failure even on nasty SATA drives with a 1 in 10^14 UBER rate. On FC/SAS drives your UBER is 1 in 10^16 and you get considerably more performance too. RAID group reliability doesn't protect you against accidental deletion. (so you need the backups anyway) beyond certain ...


8

You don't need to do anything other than replace the failed drive. There's no need to move the FSMO roles, even if DC1 is offline for a short period of time. If for some reason DC1 can't be brought back online after the drive replacement then you can seize the FSMO roles. Here's some additional info: http://www.petri.co.il/seizing_fsmo_roles.htm


8

Try: zpool detach BearCow da1 See if it spits out any error messages or resolves the issue. This should automatically happen when the resilvering is done, but it looks like yours hung for some reason. There's additional measures that can be taken if this doesn't work. It should work, but it also shouldn't be necessary in the first place.


8

Don't panic, this is a common and recoverable error. Your hosting company set up a two-disk redundant array to protect the data in case one of the disks fails. This failure has now occurred. The output indicates that sda1 has failed, and that the RAID1 array is working, but degraded. Right now you're on borrowed time, though. If the second disk fails, that ...


8

Whoever told you that RAID 10 is somehow inherently slower than RAID 1 doesn't know what they're talking about. That makes the rest of the question unanswerable as it's based on a false assumption. Further reading: What are the different widely used RAID levels and when should I consider them?


8

You can fail the /dev/sdb device through mdadm (best make sure you fail the entire device i.e. all mds that runs off it) then check it for errors, but from what you are describing you are most likely better off just replacing the device. I have had ide devices that failed on a regular basis, I kept re-adding the rejected device until finally the computer ...


8

Sort of. It is a valid test of failure (the ability of your system to keep running), but not a valid test of your controller's repair mechanism (it's ability to assimilate a replacement drive) unless you also format or otherwise wipe the disk before re-inserting it. I would test this for a scratch volume before placing it into production, and document ...


8

Yes, you can use it, it'll underperform obviously and the harder you thrash it the longer the rebuild might take but by all means use it - that's kind of the point of R1 isn't it.


7

RAID10 with 4 drives will be quicker -- the extra spindles mean that twice as many IOPS can be handled (more or less).


7

You may have misunderstood someone. RAID-5 is slower than RAID-10 on writes, but RAID-1 can be treated as a RAID-10 with a single pair of disks, and thus has the same performance per "spindle" as RAID-10. The best recommendation for SSD on a database is to use RAID-5. The rebuild time on the incredibly small and fast SSD drives is very good. Since you'll ...


7

A self-speaking excerpt from man mdadm: -W, --write-mostly subsequent devices listed in a --build, --create, or --add command will be flagged as 'write-mostly'. This is valid for RAID1 only and means that the 'md' driver will avoid reading from these devices if at all possible. This can be useful if mirroring over a ...


6

This depends entirely on the type of RAID (software or hardware) and the storage controller that is implementing RAID. I'm the vast majority of implementations, there is no service interruption to the host system (that's the whole point of RAID). There is usually some kind of notification about the failure of a hard drive that an administrator must be made ...


6

Since you created 2 logical disks, that's what you get in Disk Management. The P400 presents logical disks to Windows, not physical disks. The health you see in Disk Management is the health of the logical volumes. That will not reflect, for example, a failure of one of the physical drives. You will need to monitor that using HP Array Configuration Utility ...


6

I believe that the answer depends on the controller/software for example it is quite common for mirroring systems to only read one disc out of a pair and therefore be capable of delivering the wrong data. I note that if your results depend on that data the when the data is written to both discs it is then corrupted on both discs..... From the pdf under ...


6

I asked a NetApp engineer who was giving us a talk this very question. His answer, more or less, was: Nobody reads the checksums on reads. There's no point. Reading a checksum means you have to read the entire slice plus checksum, then compute the checksum to verify you have the correct data. Plus the orthoganal checksum if you are running ...


6

It may be better to use different brands or series of disk together if you're worried about this. I have seen disks of similar type and age fail in clusters, so IMHO it's not an urban leend.


5

To replace a failed motherboard with a new motherboard and to then reconfigure Windows to work with the new motherboard, do the following: Turn off the computer. Replace the existing motherboard with the new motherboard. Insert your Windows Server 2003 CD in the CD-ROM drive or the DVD-ROM drive, and start the computer from the CD. When you are ...


5

You can force a check of (eg) md0 with echo "check" > /sys/block/md0/md/sync_action You can check the state of the test with cat /sys/block/md0/md/sync_action while it returns check the check is running, once it returns idle you can do a cat /sys/block/$dev/md/mismatch_cnt to see if the mismatch count is zero or not. Many distros automate this ...


5

From my point this is a very bad idea, RAID 1 was never designed to be a backup solution, but a redundancy tool. That said there are tons of tools that allow you to backup a complete drive ( snapshot) which will work rather fast as well, for instance drive image XML on windows. Linux certainly has the same or similar tools available.


5

I have not yet tried the new LVM segment types, but the overview is that they are support for the Linux MD RAID personalities in LVM. That is, they are RAID levels 1, 5, 6 etc. using the MD code with the eventual goal of removing the duplicate functionality of LVM's mirroring and having both MD and LVM use the same code. This is very new stuff so may not be ...


5

This would be a poor idea overall. Vendor implementations of RAID vary, of course, so you will get different behavior with different vendors. Most assume that drives are significantly identical, so aren't designed to handle disks of such different performance characteristics. Chances are very good your performance will be handicapped by the slower disk. For ...


5

Drive "resync" occurs if a drive swap happens and the RAID is being rebuilt by the system. In RAID 1, this means copying the entire drive. You can use the OS as normal, but it's will noticeably slow and during sync you do not have redundancy as the RAID is in a degraded state.



Only top voted, non community-wiki answers of a minimum length are eligible