Here's the scoop on volumes, raid groups, parity drives, hot spares, qtrees, and root:

Volume, Raid Groups, Parity, Hot Spares-- -----------------------------------------

A volume by definition will contain one or more raid groups, just like a tray of ice can contain one or more cubes of ice.

A raid group can contain a maximum of 28 disks (one parity disk and 27 data disks). The default number of drives in a raid group is 14; that number is considered optimum for performance vs. fault tolerance. (There is data regarding MTTDL (Mean time to data loss) and other performance and mean time measures that prove 14 disks to be the optimum size for raid group.) (NetApp 202 teaches diagnostics and optimization of performance and troubleshooting.)

You can setup your 14 - 36Gb drives into one volume. But it would be better to use 13 disks in the raid group and save one disk on shelf as your hot spare. In case of failure, your filer will immediately begin to reconstruct your data to your hot spare. If you have AutoSupport turned on and configured, Network Appliance will be notified by your filer (by email) that a disk has failed and a new disk will be sent to you automatically per our service agreement. Yes, hot spares and AutoSupport are great to have working for you.)

Qtrees, security styles, oplocks, quotas, backup-- --------------------------------------------------

You can organize your one (13 drive) volume into qtrees. Qtrees are almost like separate file system partitions. Each qtree can be setup with its own set of properties. To be specific, each qtree can have its own:

- security styles (UNIX, MIXED, or NTFS) - oplocks settings (ON or OFF) - quotas for limiting users, groups or limiting the size of the qtree itself - backup and restore schedules

Snapshots are volume wide; you cannot take a snapshot of an individual qtree; however, all qtrees will be included in the volume's snapshot.

If you setup 2 volumes, you will have a minimum of 2 raid groups and therefore use 2 of your 14 - 36Gb drives as parity drives. Smaller raid groups give you greater protection against a double-disk failure, but slightly less than optimum performance and less storage space.

Also, if you reserved one disk as hot spare, it would serve both volumes. Hot spares are global to the filer and can be used in a disk failure of any volume when there are multiple volumes on the filer.)

Root-- ------

Some like to setup root as a separate 2-disk volume (parity and data disks). Having root separate helps with backup and disaster recovery and perhaps there are other considerations I don't know about. If root is a separate 2-disk volume, of your 14 disks you would have 2 parity, 1 hot spare and 11 data disks. If you have one volume with one raid group, you will have 12 data disks.

There are several other considerations about qtrees, quotas, backup, disaster recovery, snapshots and hot spares to be understood. I would highly recommend NetApp 101 and 202 for comprehensive, hands-on training on fine points such as these. You can find training schedules as well as information on NetApp Certification at http://www.netapp.com/education/#training. Also, a great place to look up technical answers is NetApp's NOW site: http://now.netapp.com/.

Best regards,

Deborah

Deborah Rousseau, MCSE, MCT Technical Trainer Network Appliance, Inc. http://now.netapp.com/

-----Original Message----- From: Brian Hostetter [mailto:BrianH@dice.com] Sent: Wednesday, June 14, 2000 8:53 AM To: toasters@mathworks.com Subject: Raid Groups and Volumes

Hello, I just got my two new 760s with 2 shelves of 36G drives each. I am going through the setup and have a question on Volumes and Raid Groups. Can I create two shelves into one big raid group in order to take advantage of all the spindles, and then create two volumes on that raid group? Or do I have to create 2 raid groups (thus using an extra parity drive) and have 1 volume living on 1 raid group.

--Brian

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