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Date:      Sun, 5 Aug 2007 18:55:27 -0700
From:      "Jeff Mohler" <speedtoys.racing@gmail.com>
To:        "Philip M. Gollucci" <philip@riderway.com>
Cc:        "questions@FreeBSD.org" <questions@freebsd.org>
Subject:   Re: Unbelievably bad RAID-1 performance
Message-ID:  <a969fbd10708051855h37264166nb831d283642aa2e9@mail.gmail.com>
In-Reply-To: <46B67C90.3010603@riderway.com>
References:  <46B67C90.3010603@riderway.com>

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The EDGE is faster byte wise, not the center.

The distance between traditional or perpendicular sectors remains the same,
just more of them around the drive at a given distance from the center, than
at the center.  So..because RPM remains the same at all distances from the
center, you will read more sectors per second at the edge, than center.

Although..that wont make a 100x difference in speed..I wouldnt think.




On 8/5/07, Philip M. Gollucci <philip@riderway.com> wrote:
>
> while writing to the disk
>
> gstat screenshot
>         http://people.apache.org/~pgollucci/disks.png
>
> If I move the location to '/' (da0s1a) which AFAIK is at the center of
> disk(smaller thus faster rpms) should be faster, performance is at least
> 100times worse which is the opposite I would expect.
>
> Is there anything I can do to help this out.  I'm likely going to chuck
> the raid card in the trash and just use one disk and reply on backups
> which I already have going.
>
> Dell PowerEdge 1435SC
>         Dual Intel Core2 Duo 2.4GHz 4GB RAM
>         RAID-1 Config with 2 disks@240GB each
>         FreeBSD 6.2-release-p5 amd64 custom kernel.
>
> mpt0: <LSILogic SAS/SATA Adapter> port 0xdc00-0xdcff mem
> 0xeffec000-0xeffeffff,0xefff0000-0xefffffff irq 35 at device 8.0 on pci7
> mpt0: [GIANT-LOCKED]
> mpt0: MPI Version=1.5.12.0
> mpt0: mpt_cam_event: 0x16
> mpt0: Unhandled Event Notify Frame. Event 0x16 (ACK not required).
> mpt0: mpt_cam_event: 0x12
> mpt0: Unhandled Event Notify Frame. Event 0x12 (ACK not required).
> mpt0: mpt_cam_event: 0x12
> mpt0: Unhandled Event Notify Frame. Event 0x12 (ACK not required).
> mpt0: mpt_cam_event: 0x16
> mpt0: Unhandled Event Notify Frame. Event 0x16 (ACK not required).
> mpt0: mpt_cam_event: 0xb
> mpt0: Unhandled Event Notify Frame. Event 0xb (ACK not required).
>
> da0 at mpt0 bus 0 target 0 lun 0
> da0: <Dell VIRTUAL DISK 1028> Fixed Direct Access SCSI-5 device
> da0: 300.000MB/s transfers, Tagged Queueing Enabled
> da0: 237464MB (486326272 512 byte sectors: 255H 63S/T 30272C)
>
>
>
>
>
>
>
> ------------------------------------------------------------------------
> Philip M. Gollucci (philip@riderway.com) 323.219.4708
> Senior System Admin - Riderway, Inc. http://riderway.com
> 1024D/EC88A0BF 0DE5 C55C 6BF3 B235 2DAB  B89E 1324 9B4F EC88 A0BF
>
> Work like you don't need the money,
> love like you'll never get hurt,
> and dance like nobody's watching.
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