On 7/7/20 8:52 AM, R.S. wrote:
Few words about RAID:
RAID is more reliable than single disk. Assuming same reliablity of disk
used in RAID.
That starts to get questionable when you have more and more disks in a
RAID array.
It's a numbers game of how likely is it to have two drives fail in a
RAID 5 or three drives fail in a RAID 6.
I think somewhere around twenty drives and you're back down to, or
below, the reliability of a single drive.
RAID6 is more reliable than RAID5. Reasons: Data on RAID6 will survive
failure of 2 drives within a group. The second reason is time to
rebuild. The more capacious disk the more time is needed to rebuild. At
this time there is no protection.
This is why I like RAID 6. I like to always have another unused safety
net, even when one drive has failed and we're relying on the 1st safety.
Side notes:
Sometimes disk failure is not just isolated case. Sometimes it is a
symptom of epidemic. What kind? Some of them: disk came form same lot,
which is bad. Earthquake or just some accident in server room (someone
hit the cabinet by accident ...and didn't reported it). Or microcode
problem (search for HP SSD - horror story).
Or very loud noises within specific frequency ranges. Fire suppression
systems come to mind.
Conclusion: when you observer disk failure, pay attention. It may be
isolated case or FIRST failure you observe.
Yep.
--
Grant. . . .
unix || die
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