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I have been reading about recommended SQL Server storage and RAID 5 or RAID 10 controllers have been recommended.

On my existing Database server I can see 4 Storage controllers under Device Manager. They are listed as... LSI Adaper (*2) VMWare PVSCSI Controller (*2)

Are these an alternative to RAID? Or should I be using RAID for SQL Server?

Thanks!

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closed as off-topic by Mark Storey-Smith, RolandoMySQLDBA, Paul White, Mike Walsh, Jon Seigel Nov 21 '13 at 18:18

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3 Answers 3

"Storage Controllers" <> "RAID". RAID is a configuration, not hardware.

For example, RAID 5 refers to having at least 3 physical disks typically attached to a disk controller such that stripes of data and parity are written across all three disks any time data is written to the array. If you had 3 x 76GB drives, a RAID-5 array would have 76 x 2 = 152GB of usable capacity since 1/3 of the total space is dedicated to parity data. The parity data is used to calculate the missing data if any one of the drives in the array fails. The RAID array looks like a single physical disk to the operating system installed on the machine.

For SQL Server, RAID-5 is typically counter-indicated since calculating and writing the parity information causes writes to be slower than with RAID-10. RAID-10 consists of at least 4 drives, 2 mirrored sets of RAID-0 arrays. Since RAID-10 does not have to calculate parity data, it is typically faster than RAID 5, and since the array is mirrored, it can survive up to 2 simultaneous drive failures. However, capacity of a RAID 10 array is smaller than a RAID 5 array consisting of the same number and size of drives.

To answer your question, no, these controllers do not by themselves mean you have any RAID at all in the system. Since the server you are looking at is a virtual machine, you would need to find out from the system administrator of the physical host machine what kind of storage it has.

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Are these an alternative to RAID?

No. They are virtual adapters from VmWare. The "Disk" cou have is a file on a file system. And without being the admin of the server (the physical one, not your virtual machine) you do not know how it is configured. It is LIKELY - a slow large disc system. But then you need to contact the admin of the physical machine to find out.

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Should you use RAID or not in I.T. comes down to if you need protection from disk failure (which is often associated with how much uptime you need and if there's critical hours which nothing can go down for more than x minuets), and performance. Without those metrics you can't answer this.

How is your current performance?

Do you know what the business uptime requirements are?

What you are seeing in the server is not an alternative to RAID, it's a VM controller that communicates to the virtual disks inside your VM. In other words it's logical. The RAID array is a physical set of hard drives. Your VM or SAN admin will have info on how protected they are, what kind of uptime SLA they can give you guys. You will have to collect perfmon metrics to see how well it is performing.

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