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We have 7 1TB disks (there is an empty slot but I'm trying to get this filled with an additional 1TB disk). I'm looking at the various merits of RAID 5 vs RAID 6 in this setup. The setups would be:
- RAID 5 with hot spare
- RAID 6 with hot spare
- RAID 6 (without hot spares)
I know RAID 6 has a performance hit although I'm unsure how much of a hit it is. I'm also trying to figure out if I need a hot spare with RAID 6 (if a spare drive is on standby to swap out as soon as drive failure noticed). If ideal, I can sacrifice 3 drives for a RAID 6 + hot spare as space isn't a major factor; redundancy and data protection is my main concern (also performance if there is a large performance difference between RAID 5 and 6).
This array will be primarily used for ESX server shared storage.
Any tips/advice would be appreciated.
Cheers,
Tim
- RAID 5 with hot spare
- RAID 6 with hot spare
- RAID 6 (without hot spares)
I know RAID 6 has a performance hit although I'm unsure how much of a hit it is. I'm also trying to figure out if I need a hot spare with RAID 6 (if a spare drive is on standby to swap out as soon as drive failure noticed). If ideal, I can sacrifice 3 drives for a RAID 6 + hot spare as space isn't a major factor; redundancy and data protection is my main concern (also performance if there is a large performance difference between RAID 5 and 6).
This array will be primarily used for ESX server shared storage.
Any tips/advice would be appreciated.
Cheers,
Tim
RobertDudley
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Posted July 21st, 2009 05:00
The rebuild times for raid6 are also longer than raid5.- I don't think I have much choice about production on SATA as it's what we've been given. What would you have chosen for this instead?
The data is going to be very valuable. It will contain all the virtual machines and the storage for these virutal machines (different LUNs for VMs and VM storage). The main criteria is that the VMs and associated storage as reliable as possible. Performance is important as VMs will be running off this but reliability is the main criteria.
Cheers,
Tim - The latest Best Practices Guide may be good read:
http://powerlink.emc.com/km/live1/en_US/Offering_Technical/White_Paper/h5773-clariion-perf-availability-release-28-firmware-wp.pdf
On page 41 it has a Raid Group section but more importantly on 41 and 42 it talks about when to use the different raid types.
-Ryan - Yeah - I'm starting to think that now as well.....
I'm a jack-of-all-trades I.T. guy who generally administers various things onsite without having too much in-depth knowledge of the technologies (the various 'teams' in our company usually decide on the technologies and there's an assumption they know best as they tend to be specialised in various areas of I.T) but I'm starting to look into these things in more detail, as it's good to know.
I noticed the SATA drives only had 7200 RPM and after a bit of digging, it's dawning on me that this probably isn't the best option for what we need. It's starting to look like they've got for a more-bang-for-you-buck approach rather than the ideal setup for the requirements.
All I've got to do now is convince them to rethink the setup........
Cheers,
Tim
RRR
6 Operator
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5739 Posts
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Posted July 21st, 2009 04:00
- RAID5 performs better than RAID6
- RAID6 is primarily meant for big SATA drives since a rebuild can take so long that the chances of having another failure before the end of the rebuild are higher than on fast and smaller FC disks. RAID6 is meant to have your data protected during the rebuild. Best practice is to have the big 1TB drives in RAID6 with an aditional HS per 15 (or 30 if using 7k2 RPM) drives.
If you only have these 7 1TB disks I can understand your dilemma. Depending on the value of your data I'd say RAID6 + HS if it's valuable, RAID6 if it's less valuable backup data or RAID5 + HS it's for "performance" data (when speaking of performance on SATA drives I always get the chills, brrrrrr).