Re: [ceph-users] CEPH over SW-RAID

Le 23/11/2015 19:58, Jose Tavares a écrit : > > > On Mon, Nov 23, 2015 at 4:15 PM, Lionel Bouton > > wrote: > > Hi, > > Le 23/11/2015 18:37, Jose Tavares a écrit : > > Yes, but with SW-RAID, when we have a block

Re: [ceph-users] CEPH over SW-RAID

So I assume we _are_ talking about bit-rot? > On 23 Nov 2015, at 18:37, Jose Tavares wrote: > > Yes, but with SW-RAID, when we have a block that was read and does not > match its checksum, the device falls out of the array, and the data is read > again from the other devices

Re: [ceph-users] CEPH over SW-RAID

Hi, Le 23/11/2015 18:37, Jose Tavares a écrit : > Yes, but with SW-RAID, when we have a block that was read and does not match > its checksum, the device falls out of the array I don't think so. Under normal circumstances a device only falls out of a md array if it doesn't answer IO queries

Re: [ceph-users] CEPH over SW-RAID

On Mon, Nov 23, 2015 at 4:07 PM, Jan Schermer wrote: > So I assume we _are_ talking about bit-rot? > > > On 23 Nov 2015, at 18:37, Jose Tavares wrote: > > > > Yes, but with SW-RAID, when we have a block that was read and does not > > match its checksum, the

Re: [ceph-users] CEPH over SW-RAID

On Mon, Nov 23, 2015 at 5:26 PM, Lionel Bouton < lionel-subscript...@bouton.name> wrote: > Le 23/11/2015 19:58, Jose Tavares a écrit : > > > > On Mon, Nov 23, 2015 at 4:15 PM, Lionel Bouton < > lionel-subscript...@bouton.name> wrote: > >> Hi, >> >> Le 23/11/2015 18:37, Jose Tavares a écrit : >> >

Re: [ceph-users] CEPH over SW-RAID

Le 23/11/2015 21:01, Jose Tavares a écrit : > > > > > My new question regarding Ceph is if it isolates this bad sectors where > it found bad data when scrubbing? or there will be always a replica of > something over a known bad block..? > Ceph OSDs don't know about bad sectors, they

Re: [ceph-users] CEPH over SW-RAID

SW-RAID doesn't help with bit-rot if that's what you're afraid of. If you are afraid bit-rot you need to use a fully checksumming filesystem like ZFS. Ceph doesn't help there either when using replicas - not sure how strong error detection+correction is in EC-type pools. The only thing I can

Re: [ceph-users] CEPH over SW-RAID

On Mon, Nov 23, 2015 at 4:15 PM, Lionel Bouton < lionel-subscript...@bouton.name> wrote: > Hi, > > Le 23/11/2015 18:37, Jose Tavares a écrit : > > Yes, but with SW-RAID, when we have a block that was read and does not > match its checksum, the device falls out of the array > > I don't think so.

[ceph-users] CEPH over SW-RAID

Hi guys ... Is there any advantage in running CEPH over a Linux SW-RAID to avoid data corruption due to disk bad blocks? Can we just rely on the scrubbing feature of CEPH? Can we live without an underlying layer that avoids hardware problems to be passed to CEPH? I have a setup where I put one

Re: [ceph-users] CEPH over SW-RAID

Le 23/11/2015 18:17, Jan Schermer a écrit : > SW-RAID doesn't help with bit-rot if that's what you're afraid of. > If you are afraid bit-rot you need to use a fully checksumming filesystem > like ZFS. > Ceph doesn't help there either when using replicas - not sure how strong > error

Re: [ceph-users] CEPH over SW-RAID

Yes, but with SW-RAID, when we have a block that was read and does not match its checksum, the device falls out of the array, and the data is read again from the other devices in the array. The problem is that in SW-RAID1 we don't have the badblocks isolated. The disks can be sincronized again as

Re: [ceph-users] CEPH over SW-RAID

-BEGIN PGP SIGNED MESSAGE- Hash: SHA256 Most people run their clusters with no RAID for the data disks (some will run RAID for the journals, but we don't). We use the scrub mechanism to find data inconsistency and we use three copies to do RAID over host/racks, etc. Unless you have a

Re: [ceph-users] CEPH over SW-RAID

On Mon, Nov 23, 2015 at 6:40 PM, Lionel Bouton < lionel-subscript...@bouton.name> wrote: > Le 23/11/2015 21:01, Jose Tavares a écrit : > > > >> >> > My new question regarding Ceph is if it isolates this bad sectors where >> it found bad data when scrubbing? or there will be always a replica of >>

Re: [ceph-users] CEPH over SW-RAID

Le 23/11/2015 21:58, Jose Tavares a écrit : > > AFAIK, people are complaining about lots os bad blocks in the new big > disks. The hardware list seems to be small and unable to replace > theses blocks. Note that if by big disks you mean SMR-based disks, they can exhibit what looks like bad blocks