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Slow performance in AutoRAID 12H

Valarie Lim

Slow performance in AutoRAID 12H

Good Evening,

I have a autoRAID disk Array which is fully populated with 18Gb 10000rpm disk.
There are six LUNs being configured.

When i run iostat between my backup timing,
the statistics shows that a maximum 3MB/s per LUN whenever reading from these LUN is needed.
When two LUN read, there is an imbalance of throughput of 7MB/s and 3MB/s.

1) May I know if the maximum throughput of AutoRAID is 10MB/s?

2) Is there anything wrong with my configuration?

David Navarro
Respected Contributor

Re: Slow performance in AutoRAID 12H


Are you using the same scsi interface for backup that LUN's?

Honored Contributor

Re: Slow performance in AutoRAID 12H

FWD scsi throughput can get up to 14MB/s if you're lucky.

As mentioned, check your lun access configuration (LVM)

arraydsp -c
where is returned from arraydsp -i
Mark the controller SCSI IDs from the output.

ioscan -fnkCdisk
will show you the paths to the LUNs. If you have two controllers you will have two access routes to the LUN. One throu X and the other thru Y.

Access half through X and the other half through Y.
This is done via LVM vg configuration:

strings /etc/lvmtab

c1t2d1 LUN1 thru t2 (scsi id 2)
c2t3d2 LUN2 thru t3 (scsi id 3 on a different bus - c2)
(It doesn't necessarily have to be a different bus but you're not sharing bus bandwith if it's like this)

So you access LUN2 through a different controller (and bus) than LUN1 and can realistically get up to 14MB/s simultaneously.. giving 28MB/s transfer to the array.

Note that the LV, thus the filesystem) can be spread across those two LUNs (which are LVs) using the lvcreate -i 2 -I 64 option.
Thus your filesystem can get faster than rather having your LV on one PV only
lvcreate -L 500 /dev/vgauto
only one PV for the lvcreate here. (well if there's not space on the PV1 (LUN1) it will continue onto PV2 (LUN2))


It works for me (tm)
harry d brown jr
Honored Contributor

Re: Slow performance in AutoRAID 12H

The performance specs are a max of 20mb/s:


Do you have ONE or TWO controllers? If you have TWO, do you have alternate pathing (use seperate IO path) to the device (disk/lun) per VG?

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