At Sat, 27 Mar 2010 11:01:08 -0700 CentOS mailing list centos@centos.org wrote:
Pasi Kärkkäinen wrote:
On Fri, Mar 26, 2010 at 11:14:18AM -0700, Benjamin Franz wrote:
Yup. 8 way RAID1 for the OS, 8 way RAID6 for the data. I was hoping when I setup the 8-way RAID1 for the OS that I would get really good read speeds since md is supposed to stripe reads from RAID1, but in practice the RAID6 completely kills it for read performance (~61 MB/sec from the RAID1 partition vs ~200 MB/sec from the RAID6 partition).
In a deeply ironic turn of events, one of the hard drives in that machine died in a way that freaked the hardware controller driver out and caused a kernel panic last week.
I've also seen CentOS 5.3 (or 5.4, not sure) crash when a single sata hdd failed. The system was running mdadm RAID-1 mirror, so it shouldn't have been fatal event..
There was kernel oops on the console. too bad I didn't have time to capture it then. System was running AHCI SATA on Intel ICH9 controller, with mdadm software raid.
So there's still need for hardware RAID controllers..
I'm not sure that is a good conclusion. The controller *is* a (3ware) hardware RAID controller - but the drive failure caused the 3ware driver to crash. That I wasn't using the controller in HW RAID mode may not be a good indicator that all would have been well if I had been.
There might be drive failure modes that put the drive controller into an 'odd' state. Still should not cause the software driver to crash -- I'd consider that a software bug. I've never heard of a SCSI HBA driver crashing. I might have encountered drive failure modes that would do things like hang the SCSI bus or otherwise confuse the SCSI HBA (eg causing it to fail to see *other* drives/devices). Since there is no SATA 'bus' (SATA drives are connected point-to-point 'star' fashion), a failed drive should not take the controller out, but I guess it depends on the signaling logic and what sort of logic gates are used for 'drive select'. Of course, a controller like the 3ware hardware RAID controller, configured in JOBD mode, probably looks like a SCSI HBA with bunch of disks on a single SCSI bus.