Re: Bad Hardware / Software Disk Detection for Production Systems

[Mark Nipper <nipsy@bitgnome.net>]

On 02 Jun 2006, Bill Rees wrote:
>    This is a general question but I thought I'd post it to the list to see if
>    anyone has any suggestions.

        You cannot expect any sort of data integrity if you are
using JBOD mode on a RAID controller.  The very nature of JBOD
means that any time a single drive fails, you lose every
partition across that entire JBOD volume.

        If your file systems are even coming back after such a
catastrophe, you have been extremely fortunate to date.  I still
cannot imagine that you aren't losing data though since there is
no mirroring going on whatsoever which means blocks are
inherently being lost during such failures.

        If you are just looking for read performance, you should
seriously consider at least a RAID 1 volume.  If you can
sacrifice some overall performance, you will get the best space
optimization by going with a RAID 5.  Anything more exotic than
that, you should start at:
---
http://en.wikipedia.org/wiki/Redundant_array_of_independent_disks

and go with whichever level of RAID makes the most sense for your
application.

        The bottom line is, you are going to lose data in a JBOD
array (unless you also happen to be doing some sort of software
RAID on top of that).  There is really no gain through some sort
of software trick to try to avoid the data loss.  SMART enabled
hard drives may occasionally warn you of an imminent failure, but
then again, they may not.  Drives will just occasionally fail
entirely without any warning, hence the whole purpose of RAID
levels above 0.

-- 
Mark Nipper                                                e-contacts:
832 Tanglewood Drive                                nipsy@bitgnome.net
Bryan, Texas 77802-4013                     http://nipsy.bitgnome.net/
(979)575-3193                      AIM/Yahoo: texasnipsy ICQ: 66971617

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