Striped datasets

[Lawrence Czlapinski]

Robert Gezelter: RAID may allow you to make a striped set of two but it doesn't make any sense to create a striped set of two even if it were allowed. "Generally, for 2 disks you would use shadowing (also called mirroring) rather than striping." I never said striping was the same as shadowing (or mirroring).
Lawrence

[Robert_Boyd]

Lawrence,

A 2 member stripe set has almost the full capacity of the combined available capacity of the 2 stripeset members. A 2 member shadowset has only the capacity of the smallest of its 2 members available. There are people who use 2 member stripesets -- regardless of whether or not this makes sense from a reliability standpoint.

Personally, I would rather have a combination that is more reliable, like a stripeset of members made up of shadowsets or raid5+3 raidsets for a "plaid" arrangement. I prefer that when using raid to build up multidevice virtual volumes that that they be able to survive the failure of a single physical device and allow for hot replacement of that device.

Robert

[Lawrence Czlapinski]

Robert Gezelter: I assumed that Dudley is running in a Production environment. RAID 0+1 may allow you to make a striped set of two but it doesn't make any sense to create a striped set of two on a Production system even if it were allowed. "Generally, for 2 disks you would use shadowing (also called mirroring) rather than striping." I never said striping was the same as shadowing (or mirroring). We don't use 2 disk striping on development systems either because we often use our development systems as spares for production systems.
Running Raid 0 in a Production environment is a single point failure waiting to happen unless the disks are also shadowed. In this instance there is no indication that the disks are shadowed.
Lawrence

[Lawrence Czlapinski]

Robert Gezelter: I strongly agree. I was not precise enough in what I was talking about.
Lawrence