27 Mar
2018
27 Mar
'18
6:26 p.m.
On 2018-03-27 10:05 PM, Ali via cctalk wrote:
-------- Original message --------
From: Fred Cisin via cctalk <cctalk at classiccmp.org>
Date: 3/27/18 5:51 PM (GMT-08:00)
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
Subject: RAID? Was: PATA hard disks, anyone?
How many drives would you need, to be able to set up a RAID, or hot
swappable RAUD (Redundant Array of Unreliable Drives), that could give
decent reliability with such drives?
10 -
Two sets of 5 drive? RAID 6 volumes in a RAID 1 array.
You would then need to lose 5 drives before data failure is imminent. The 6th one will do
you in. If you haven't fixed 50 percent failure then you deserve to lose your data.
Disclaimer: this is my totally unscientific unprofessional and biased estimate. My daily
activities of life have nothing to do with the IT industry. Proceed at your own peril.
Etc. Etc.
-Ali
To meet Fred's original criteria you would only need 4 to create a
minimal RAID 6 array.? In theory a RAID 1 array (mirrored) of 4 or more
disk could also survive a second disk failure as long as one copy of all
the pairs in the array survive but you are starting to play the odds,
and I know of some cases where people have lost . You can improve the
odds by having a hot spare that automatically take over for a failed
disk.? One of? the most important things is the array manager has to
have some way of notifying you that there has been a failure so that you
can take action, however my observations as a hardware support person is
that even when there is error notification it is often missed or ignored
until subsequent failures kill off the array. ? It also appears to be a
fairly common notion that if you have RAID there is no need to ever
backup, but I assure you RAID is not foolproof and arrays do fail. ? One
of the big problems facing using large disks to build arrays is the
number of accesses just to build the array may put a serious dent in the
speced number of accesses before error or in some cases even exceed it.
Paul.