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[ale] backup/restore mail from USB external drive



On 02/12/2014 06:43 PM, Ray Vastly wrote:
> Why should you avoid raid 5 or 6 when using large hard disks? What Raid
> configuration would you recommend for 12 HDDs each 2 TB in a NAS?

My personal opinion?

Backups, then
RAID10, then
RAIDz2, then
RAID1, then
RAIDz

A few years ago, it was believed that large drives had an issue with MTBF such
that it was likely that after replacing a failed HDD another drive would fail
during the RAID-rebuild. I haven't seen anything recent to prove or disprove it.
I do know that drive warranties have changed from 5 yrs, to 3 yrs to 1 yr over
the same period. Many USB drives people buy to backup stuff at home have 90 day
warranties. Buyer beware.

When I upgraded from 4x320G RAID5 to 4x2TB disks, I switched to RAID1. I still
do weekly RAID scrubs and nightly backups.  I'd never experienced the
RAID5-hole, but didn't want to either.

BTW, 1 of those 2TB disks failed last week after 16 months in-service.


> 
> On Feb 12, 2014 6:40 PM, "Jeff Hubbs" <jhubbslist at att.net
> <mailto:jhubbslist at att.net>> wrote:
> 
>     On 2/12/14, 5:00 PM, Lightner, Jeff wrote:
>>     <snip>____
>>
>>     __ __
>>
>>     You really should be using RAID6 or RAID10 rather than RAID5 as it is even
>>     more redundant (i.e. can survive 2 disks failures). 
>>
>     And you shouldn't be using RAID5 or RAID6 at all if your drives are
>     750-1000GB or larger. 
> 
>     Mail and database servers would be two good places to make use of
>     snapshotting filesystems.  Note that some email systems that use message
>     stores go insane if the message store is not in the state that the rest of
>     the email system presumes it's in, so you have to make sure that your
>     backup/recovery scheme doesn't capture messages and message metadata/index
>     in different states.
> 
> 
> 
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JD Pflugrath
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