installed DS2405, what's the best config

[Joe Hege]

I've got a ds2405 jbod connected to 2 fiber cards with 8 drives. What's the best LVM setup? The DBA wants me to mirror 1 to 1. Do I create 2 physical volume groups, 4 disks each or 1 volume group with all 8 then mirror 1 to 1. Just trying to get the best redundency

Thanks
JOe

[S.K. Chan]

Yes that's what I'll do, create 2 PVGs, one set of disks which are on say channelA in one PVGA and the rest in the other PVGB. Mirror your lvols in PVG-strict mode. That way you can be sure that your mirrored copies always reside in PVGB, thus making recovery easier and much cleaner.

[Pete Randall]

First, do you have the MirrorDisk/UX product installed? You're going to need it.

Second, mirroring is done on a logical volume basis within the same VG. I would go for 1 VG with all 8 and mirror each LVOL within.


Pete

[A. Clay Stephenson]

The "best" configuration is probably the "delayed" configuration. If this were me, I would only configure the minimum number of physical drives with 1:1 mirroring in the same VG. The mirrors should utilize separate buses. If your drives are of different sizes then start the VG using your largest physical drives so that when you need to vgextend all the extents on the new disks can be used. Using the "delayed" approach gives you the flexibilty to change in the future. It's trivially easy to extend VG's, LVOL's,m and filesystems (assuming you did purchase OnlineJFS); moreover, DBA's who really know what they need on the front-end are rather rare.

Given that's its much easier to add to a VG rather than taking away from the same, I would allocate as little as possible (with reasonable headroom) at this juncture and then, as needed, extend when you have operational data.