Got a call at 4am - RAID Gurus Please Read

Seth Mos seth.mos at
Wed Dec 10 08:49:57 UTC 2014

symack schreef op 9-12-2014 22:03:
> * Can I change from an active (ie, disks with data) raid 5 to raid 10.
> There are 4 drives

Dump and restore. I've used Acronis succesfully in the past and today,
they have a bootable ISO. Also, if you have the option, they have
universal restore so you can restore Windows on another piece of
hardware (you provide the drivers).

> in the unit, and I have two on the shelf that I can plug in.
> * If so, will I have less of performance impact with RAID 10 + write-thru
> then RAID 5 + write through

Raid10 is the only valid raid format these days. With the disks as big
as they get these days it's possible for silent corruption.

And with 4TB+ disks that is a real thing.  Raid 6 is ok, if you accept
rebuilds that take a week, literally. Although the rebuild rate on our
11 disk raid 6 SSD array (2TB) is less then a day.

If it accepts sata drives, consider just using SSDs instead. They're
just 600 euros for a 800GB drive. (Intel S3500)

> Given I can move from RAID 5 to RAID 10 without loosing data. How long to
> anticipate downtime for this process? Is there heavy sector re-arranging
> happening here? And the same for write-thru, is it done quick?

Heavy sectory re-arranging, yes, so just dump and restore, it's faster
and more reliable. Also, you then have a working bare metal restore backup.



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