Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
On 23.07.2014 23:42, Robinson, Eric wrote: >> Sounds like you want to run Raid1 (drbd) over Raid0 (ssd+md?). This is more fragile than Raid0 >> over Raid1, so you might consider implementing Raid0 using DM over multiple drbd devices, >> each mirroring a single ssd. > >> Andreas > > > Our plan is to implement Raid0 using Intel hardware RAID controllers on each server, then Logical Raid1 would be provided by DRBD between the servers. My thought was that if anything happens to a RAID volume, DRBD would simply detach and start using the volume from the other server. No? > Yes, but there are two issues with this: a) Once you replaced the failed drive you have to re-sync the entire Raid-0. b) If a single drive fails on system b before you replaced and re-synced system a your data is gone. If on the other hand you build multiple DRBD mirrors with a Raid-0 on top: a) you only have to resync a single drive which is faster and doesn't impact the performance of the other mirrors. b) you only lose data if the other drive of the degraded mirror fails. If any other drive fails your data is still fine. So while the "Raid-0 over multiple DRBD mirrors" setup is a bit more finicky to handle it provides significantly higher reliability and faster rebuild times. Regards, Dennis