RAID 5 for combined OS and Data Volumes....Bad Idea?
Posted on 2009-07-15
Basically I work for a company which provide software which requires a database servers. The standard set-up for these server's is always RAID 5 using some like 5 physical disks and 1 hot spare.
We then partition a C and D drive across the RAID container, OS on C: drive and the data on D: drive
I encountered an issue the other day when one of the disks on the RAID failed - Windows blue screened and crashed. On trying to reboot the server reported "Unable to find bootable device" which would suggest no MasterBootRecord could be found.
We then added the hotpspare to the RAID5 and let it start rebuilding from parity bits. Whilst it was rebuilding at got to around 7% and 10% rebuild, we tried rebooting and received the same "Unable to find bootable device". We eventually waited for the disk to fully rebuild and then Windows would boot up with no problems.
Now, having the OS volume and the data volume on the same RAID is normally bad idea in my opinion....Would you agree and that RAID 1 for the OS and RAID 5 for the data volume would be better and if so, why?
I presume the OS crashed and wouldn't load because elements of the OS were held on this faulty disk which failed, and would only boot when it had rebuilt and could access what is needed again...however isn't RAID 5 supposed to provide this data using parity bits whilst the disk is faulty or rebuilding?