HPE Storage Users Group

Accordingly best practice documentation RAID-5 is not recommended for NL drives.
But reason is not explained. Why ?
By default for NL drives available only RAID-6.
In google I found information that the main reason why you need to go with RAID6 on NL drives is because of the time it takes to rebuild a large drive once it fails. Is it only reason ?

Its mainly the size that creates the issue, but there is another factor.

most 3-4 TB enterprise drives have a non-recoverable read error for every 1 sector per 10^15 bytes.

compared to fx. a 1.2TB 10k 2.5" drive, which has a rate of 10^15.

ive personally had a raid 50 have a non-recoverable read error when when doing a rebuild (on a equallogic array), i was very fortunate, but it could have meant that we would have had to do a full recovery from backups.

With 3par in particular, it makes me wonder a bit more though, since all raid sets are made from small 1GB chuncklets, it should not have the same impact, when doing a rebuild, compared to doing a full rebuild of a physical disk (depending on amount of disks etc.). Raid-MP and Raid-6 might more be a "checkmark" function for 3par, so they can fullfill requirements of raid-6 in offers.

If one of the Guru's could enlighten, it would be appreciated.

Hi,

We have recently integrated the M6720 enclosure with 4TB spindles into one of our existing environments (7200 + M6710, 48x300GB SAS FC 15k) for backup/virtual copy/full copy purposes.

Initially I thought about RAID6 for the new NLs (as per HP best practise guide), although what worries me is performance drawback during normal operation as well as during 1 or 2 disk failures/rebuild (I imagine that it can take ages).

I wonder if someone has any experience in this area?

I also think about RAID10 and sacrifice the available capacity for the performance.

IT is the rebuild times, you can override that from the CLI. We use Raid5 for our 2TB drives and have not had a problem, if I had larger drives Iw oudl opt for Raid 6. If I had the time to convert my NLs to Raid 6 I would.