afrefa.blogg.se - Best softraid 2017

Best softraid 2017 software#
Best softraid 2017 code#

This is due to the possibility of a 3 way vote between data, parity 1, and parity 2. For RAID 6 - only if the error is in one of the parity blocks.

By using a forward error correction style voting system.

Best softraid 2017 code#

RAID 6 and RAID 1 arrays with at least 3 disks are the only standard RAID levels that have the potential to be able to detect and correct some forms of silent bit rot that are not reported by the individual disks as errors, though I do not know if mdadm implements the required code for this. the server lost power before it had written its data to all of the disks in the array, then some blocks in that stripe will be in disagreement with the others.Īnd other types of errors such as those described on the ServerFault page Is bit rot on hard drives a real problem? What can be done about it?.Reading the block that was actually written will report that it read the block just fine, even though it is not. if there was a head positioning error during a write so some random nearby sector is overwritten with data and correct ECC data for that block.However there are still risks to your data that will not result in any error being reported by the disk such as This is why most bit rot will be reported as an Uncorrectable Read Error (URE) by the disk systems to mdadm. See this wikipeadia article for some info on how HDDs do this, in particular note the use of Error Correction Coding (ECC).

Best softraid 2017 software#

All RAID 1 controllers, be they software or hardware, rely on the fact that HDDs use their own error detection and correction methods.

Linux mdadm adds some array description to the start of the disk so it can know which partitions belong to what array, so mdadm will know it was a RAID 1 but can mount and use the single disk anyway. If you take a disk out of any RAID 1 and use it in another PC, it will very likely just work as a normal single disk. It adds no error correction or detection data.

Linux mdadm RAID 1, like nearly all RAID 1 implementations, is just duplicating/mirroring the same data on to multiple disks.

RAID 5 cannot do even this during a rebuild of a failed disk, this is what most concerns these days are with RAID 5. Silent bit rot detection with any standard RAID can only occur during data scrubbing. Note that not all drives in a RAID5 stripe are read from for a normal data read, so if the error exists in the stripe on the unused disk it will go undetected until you perform a data scrub. Though it will be able to correct a single block that has been reported by the disk as having an Unrecoverable Read Error (URE). Even RAID 5 will not be able to correct silent bit rot, but it can detect it during a data scrub.