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43121
April 16th, 2015 18:00
Sliced RAID on PERC H710
I am looking to deploy a sliced RAID 5 (Ie; 3 Virtual Disks across 8 physical disks), but wasn't sure on if the disks and redundancy of the RAID will fully protect my data. Are their any caveats to doing this other than the obvious not being able to expand the RAID later?
Thanks all!
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theflash1932
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April 16th, 2015 22:00
Not being able to expand the array is certainly one downside. In some cases, although due to a level of complexity rather than by design, in the event of a drive failure, the replacement disk may not rebuild all of the slices. To help prevent this, it becomes very important to keep your RAID controller (and system firmware) and HDD firmware up to date. This type of failure is also more common with some non-certified drives, especially desktop or NAS drives (which shouldn't be used in servers anyway).
jman87
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April 18th, 2015 00:00
Is this problem with rebuilding the RAID mostly if you have a mixed RAID slice setup? For instance, two virtual disks, one at RAID 5 and one at RAID 0?
My though was that we would be able to lose the one disk still and remain online (still true with the sliced RAID I would imagine?), and let the RAID rebuild to the hot spare.
I know Dell used to ship their servers with multiple RAID slices if you ordered over 2TB in a RAID higher than 1.
Let me know what you think?
theflash1932
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April 20th, 2015 08:00
Yes, rebuilding simultaneous RAID array is a very advanced function, so it is more prone to issues. There should be no issues rebuilding a single RAID array across the disks. Whether sliced or not, redundancy should remain intact, according to the RAID level chosen.
You cannot mix RAID levels across the disks; if you want to create slices, they must all be the same level. Software RAID is usually the only type that will allow mixing of RAID levels (like RAID 5 and 0).
Yes, they did/do - 1) when non-UEFI setup is selected, or 2) on server models or operating systems that did not support UEFI at all.
jman87
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April 21st, 2015 22:00
So say I wanted to Expand/change RAID level later on. Can I just delete one of the Virtual Disks, and I will be able to perform an expansion/reconfig of RAID level?
Or, do I need to blow away all Virtual Disks?
theflash1932
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April 21st, 2015 23:00
Depends. You can change one RAID level to another ONLY as long as you are not taking any disk space away from the array. For example, you can go from:
etc.
But, you cannot go from:
etc.
You also cannot go TO or FROM a nested RAID level (RAID 10, 50, 60).