Raid recommandation for Hyper V

I have some questions about Raid configuration with Hyper V :

- Is it better to create a raid 1 of 2 disks for Host OS with HyperV and another RAID (5 or 10) for VHDs ?
- one array with several raids for different kind of VMs (mix of raid 5 and 10) ?
- Difference between Raid 5 & 10 ? Raid 5 for file server and Raid 10 for database & exchange ?
SA-ITAsked:
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Cliff GaliherCommented:
It really depends on the environment. The more spindles in an striped array, generally the better the performance. But carving up storage allows for better space management, monitoring, and organization. RAID 10 will usually perform better than RAID 5, but as you get less usable space, that comes at an increase in cost per gig. Then there is a question of management. An environment with SCVMM and SCOM can have very different use cases for handling faults than a shop without 24-hoir monitoring and automated recovery processes.
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DavidPresidentCommented:
Look, it is real simple
1. RAID1/10  provides higher IOPs, at a penalty of higher cost because you need more disks.
2. If you lose a disk in RAID5 vs RAID10 configuration, you will suffer a significanty higher performance hit while it is degraded, and it will take much longer to rebuild the array, since all disks will have to be read in the process.

The delta between performance is a function of the # of disks, your controller, the nature of your I/O, and some configurable settings.  You could see 50% hit, or 500% hit as example.

Traditionally, the best bang for the buck, is to go with a RAID1 for your O/S, swap, and scratch table space, and DB index files.  Then go RAID5 (or RAID6) for your database itself. This is a good balance.  If budget allows, do RAID10 instead of RAID5 if you care about performance.   Go RAID6 instead of RAID10 or RAID5 if downtime and data loss is unacceptable.
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rindiCommented:
Never use RAID 5, in any environment. RAID 5 us unreliable, and you can make too many mistakes with it. RAID 5 was OK a decade ago or so, when disks were of low capacity and terribly expensive, with RAID 5 you were able to get the best capacity out of the minimal number of disks. Today's disks are much larger so capacity shouldn't be an issue. All other RAID's (except RAID 0), are superior.
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Philip ElderTechnical Architect - HA/Compute/StorageCommented:
We will never deploy RAID 10 since we lost a server due to one drive failing then its pair failing about five minutes after the hot swap process.

We have an EE Hyper-V Hardware and Software Best Practices Guide.

RAID 6 with as many spindles as can be afforded. Smaller sizes with more quantity yields the best IOPS depending on workloads.
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DavidPresidentCommented:
Never forget that 100% of disks fail ... eventually.  Not even RAID6 protects against data loss in all situations.    (Especially when dealing with human error). That is why a redundant RAID should never be a substitute for backups.   I do, agree that RAID6 is much better than RAID5, and as for RAID10.   I personally do 3-way mirroring to avoid such things.
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SA-ITAuthor Commented:
Is it a good configuration to use a raid 1 of 2 disks for Host OS and a RAID10 of 4 disks for VMs (VHDs) ?
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SA-ITAuthor Commented:
Or do you recommand to create an array of 6 disks within a small RAID10 for Host OS, a big RAID10 for Exchange & Apps server and a RAID5 for AD/fileserver ?
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rindiCommented:
As I already mentioned, don't use RAID 5 in any configuration. Other combinations are fine.
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SA-ITAuthor Commented:
Ok I think I will use a configuration with a RAID10 of 6 disks (with host OS & VMs).
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DavidPresidentCommented:
a 6-disk R10 will be fine.  BUT .. you have the potential of getting significantly more IOPs with a 2-disk RAID1 and a 4-disk RAID10.     That is because you can have a smaller chunk / NTFS and I/O size on the RAID1.  The native NTFS SQL Server I/O size is 64KB, you can insure the RAID controller and file system have same I/O sizes of 64K with a 2 and 4 drive RAID1/10 respectively.    You can't do that with a 6-drive RAID10 .
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Seth SimmonsSr. Systems AdministratorCommented:
This question has been classified as abandoned and is closed as part of the Cleanup Program. See the recommendation for more details.
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