Date: Sun, 13 Aug 2000 17:35:22 +0200
From: Hubert Tonneau <[EMAIL PROTECTED]>
This a report about real production experiment using both Linux
software RAID and a Mylex hardware RAID controler (real production
tend to be even harder than tests, even on a lower load, since
more special situations append).
My production server has:
2 x 8GB linux software RAID 1, Buslogic BT958 controler (ultra wild SCSI 40 at MB/s).
4 x 45GB linux software RAID 5 (0 spare), Buslogic BT958 controler (ultra wild SCSI
at 20 MB/s).
6 x 50GB hardware RAID 5 (1 spare), Mylex AcceleRAID 250 (ultra wild LVD SCSI at 80
MB/s, also called ultra2 SCSI).
All cables are short, high quality, and the all server is connected to an UPS.
There is also an air cooler to prevent excessive heat.
[snip]
So, the final unanswered question is why did the Mylex controler failed
that ungracefully if no disk contains dead blocks ?
My experimental conclusion is that Linux software RAID is even more
reliable (the two RAID sets handled by Linux sofware had no problem since
I use the right conservative bus speed), and much more flexible (enabled
me to check disks individually, and freely select the right RAID 5
configuration to match existing datas).
Thanks to Ingo and others for this great work.
Generally, the Mylex PCI RAID controllers take disks offline when certain types
of unrecoverable errors occur. The driver will log the reason for any disk
being killed as a console message. Without further information as to precisely
why the disks were taken offline and whether they all were taken offline
simultaneously, it's hard to know what happened. Firmware bugs in either the
controller firmware or disk drives are a plausible reason, as would be a
problem with the SCSI controller chip on the AcceleRAID, or an electrical
problem on the SCSI bus.
Leonard
