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Re: [linux-lvm] Can I create a PV that only uses a portion of a partition?

On Tue, 11 Mar 2008, Marek Podmaka wrote:

> I didn't have md failure on recent kernels... now the reboot while
> syncing is possible? On older kernels it just started from the
> beginning.

Yes, recent kernels keep a sync status in the raid superblock.

> But this approach has a performance penalty - from the md raid1 kernel
> sources it seems that it does try to optimize reads (choose from which
> of the mirrored drive to read block), but it does not work with multiple
> md devices on the same disks (each md has its own information about
> the current position of drive heads and doesn't know that the md is
> also "using" the same drives).

Mirroring of any description is fairly pointless unless the mirrors
are on separate devices.  Not only for performance, but because the
main point is to protect you from single disk device failure.

	      Stuart D. Gathman <stuart bmsi com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.

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