DANGER!!! Problems with 10.04 installer (RAID devices *will* get corrupted)

CLIFFORD ILKAY clifford_ilkay at dinamis.com
Fri Apr 23 15:34:47 UTC 2010

On 04/23/2010 08:03 AM, Karl Larsen wrote:
>           I will never use raid because I am not running a server. But
> even if I was I would back up the server every night using cron. It is
> the only thing to do if you have important data.  People on this list
> have real pain when there hard drive fails (or the RAID5 system acts up)
> and I feel their pain but it can be solved ONLY by a real back up.

Doing backups would be the right thing to do because RAID is NOT a 
backup solution. It is a fault-tolerance and in some cases, a 
performance solution. With the right hardware and the right 
configuration, RAID enables your machine to continue working even after 
a drive, two in some configurations, fails and again with the same 
criteria, you can get better performance. That is essential for servers 
that must have high availability or special needs like having fast 
database read times. If you have a hot swap device, you can replace the 
defective drive without powering down and the RAID set will rebuild. 
Performance during the rebuild will be reduced but lower performance 
usually is better than being off-line. Before the dead drive in the RAID 
set has been replaced and during that rebuild process, you have a 
vulnerability window in most RAID configurations where failure of one 
more drive will break the RAID set. That's why it's important to have 
spare drives on hand to replace the failed drives as soon as possible.

Someone mentioned using SATA drives for RAID. Beware. Many, perhaps 
most, of the consumer grade SATA drives aren't suitable for using in 
RAID. The drive manufacturers have made firmware changes that prevent 
them from being used in RAID configurations, apparently. Western 
Digital, for example, has their consumer drives, which have three year 
warranties, and their "professional" drives, which have five year 
warranties. The pro drives are at least double the cost of the consumer 
drives but they're RAID-certified and have different firmware. I have no 
idea what happens if you use a consumer drive in a RAID configuration. 
It might work but not optimally.

Clifford Ilkay
1419-3266 Yonge St.
Toronto, ON
Canada  M4N 3P6

+1 416-410-3326

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