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Hatton, Peter wrote: | | Anyway, I was saying earlier I intend to upgrade the P233 server box, my | intention is to have pair of new hard discs and mirror them using software | raid. But I can't see how I can use LVM2 and Software raid together? Is it | possible?
The HOWTO seems to suggest building RAID 1 or RAID 1/0 arrays, and them placing the /dev/mdX devices under LVM.
I don't recall this being how it was done on the LVM2 presentation I went to - but since I used to run HP-UX LVM on hardware RAID it seems not an unreasonable approach.
In these scenarios I think the root device is usually /dev/md0, i.e. a RAID 1 pair (or more), and not under LVM.
Then disks of the same types - a selection of RAID 1/0 arrays - are placed in a vgraid1 - and you allocate your requirement for RAID space from this volume group.
Whilst I was very impressed with the LVM2 tools, unless you are handling a lot of disks, or have keen high availability requirements (i.e. down time is not an option when adding/adjusting storage), it is overkill.
In most such scenarios you'd be using hardware RAID arrays - as most PC's (including servers) just don't have room for the number of disks to justify the use.
Even the 20 disk HP-UX box I did most of my RAID fun on had virtually all these disks configured as 4 logical devices (2 x RAID 5, 2 x RAID 1) and so could have been reasonably managed without LVM - although since it was available it was used. For stupid historical reasons most of these arrays were in one volume group, and logical volumes were forced to use specific "physical"(read RAID array) disks at creation time.
These days I would just configure a selection of RAID 1/0 arrays, and stick them all in one volume group - ala SAME (striping and mirroring everywhere). The magic if any done in the file system mounting options on the logical volumes - where filesystems are needed/preferred.
Although these days your high end hardware RAID devices will probably suggest you let them deal with such grubby details as how to store and where to store data to disk, and they will probably do it better than you could and tune it as it discovers how the disks are used.
Come back tldp.org all is forgiven... -----BEGIN PGP SIGNATURE----- Comment: Using GnuPG with Debian - http://enigmail.mozdev.org
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