I'm ramping up on zfs and related topics and fiddling around with my vmware sandbox version before i create a new system and migrate . I was reading cyberjock's FreeNAS guide for nubs (me). I saw this:
"If your VDev has only 1 disk of redundancy(RAIDZ1 or RAID1) and you have to replace
a failed disk and any other disk has even 1 bad sector you are literally running a RAID0(striped pool) until the rebuild is complete. Statistically you can also expect some ZFS corruption and data loss. The data loss can vary from a single file to complete file system corruption resulting in loss of multiple files or metadata. This is not a limitation of ZFS but is a limitation of having only 1 disk of redundancy."
By extrapolation doesn't this mean the with RAIDZN if you lose N disks *and* any other disk has 1 bad sector you are guaranteed loss? This would seem like big deal, to the point where i would just say RAIDZN is trashed in freenas (and not degraded) as soon as you have lost N disks. Maybe i am missing something here, unless a bad sectors on those remaining disks is particularly rare, but that would make RAIDZ2 only good for 1 disk loss, and RAIDZ3 good for 2 disk loss.
Is there any way to increase the parity storage by default so that you still have some wiggle room on the remaining disks in the vdev when you have lost N disks?
Thanks !
"If your VDev has only 1 disk of redundancy(RAIDZ1 or RAID1) and you have to replace
a failed disk and any other disk has even 1 bad sector you are literally running a RAID0(striped pool) until the rebuild is complete. Statistically you can also expect some ZFS corruption and data loss. The data loss can vary from a single file to complete file system corruption resulting in loss of multiple files or metadata. This is not a limitation of ZFS but is a limitation of having only 1 disk of redundancy."
By extrapolation doesn't this mean the with RAIDZN if you lose N disks *and* any other disk has 1 bad sector you are guaranteed loss? This would seem like big deal, to the point where i would just say RAIDZN is trashed in freenas (and not degraded) as soon as you have lost N disks. Maybe i am missing something here, unless a bad sectors on those remaining disks is particularly rare, but that would make RAIDZ2 only good for 1 disk loss, and RAIDZ3 good for 2 disk loss.
Is there any way to increase the parity storage by default so that you still have some wiggle room on the remaining disks in the vdev when you have lost N disks?
Thanks !