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performance writing to an lv with no file system

linux-lvm Howard Clifford 2 participants 2 messages Jun 30, 2003 – Jul 1, 2003

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Howard Clifford

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#0 lore raw

Heinz,

Thank you for the response.

My logical volume is striped - 7 ways.

I am writing to the lv with a simple c program I wrote.

Each write is 7*stripesize, which in this case is 28 blocks.

Any thoughts on how I can get top speeds without mounting and unmounting
the volume?

Thanks,
Howie

Quoted 7 lines

Howard,

what's the LV layout (linear/striped ?).
How do you write to the LV (dd or soemthing). What's the write pattern (sequential ? block size ?)

80MB/sec raw sounds like you use a striped LV.

Quoted 24 lines · Howard Clifford

I built a 7 disk vg and put 1 lv on it. I do not want to mount a file system.
I just want to write directly to the disk device, /dev/vg1/vol1.

My write performance has an odd behavior.
If after booting I write to the volume I get roughly 175MB/sec. If after booting I do a mke2fs on the volume, mount it, umount it, then write to the volume I get roughly 230 MB/sec.

Any ideas? How can I get top speed without first mounting then umounting the volume?
By the way, I tried binding a raw device to the lv and got very bad performance; around 80 MB/sec. Would that be expected?

(I'm using redhat 9.0 -> lvm-1.0.3-12)

Thanks...

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Signature · 15 lines
Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
[email protected]                           +49 2626 141200
                                                       FAX 924446
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#1 lore raw

Howard,

the raw throughput you report is likely caused by io bus saturation and as Patrick mentioned the variation by caching.

Check your io configuration if saturation is an issue.

Regards,
Heinz -- The LVM Guy --

Quoted 43 lines · Howard Clifford

Heinz,

Thank you for the response.

My logical volume is striped - 7 ways.

I am writing to the lv with a simple c program I wrote.

Each write is 7*stripesize, which in this case is 28 blocks.

Any thoughts on how I can get top speeds without mounting and unmounting
the volume?

Thanks,
Howie

Quoted 7 lines

Howard,

what's the LV layout (linear/striped ?).
How do you write to the LV (dd or soemthing). What's the write pattern (sequential ? block size ?)

80MB/sec raw sounds like you use a striped LV.

Quoted 16 lines · Howard Clifford

I built a 7 disk vg and put 1 lv on it. I do not want to mount a file system.
I just want to write directly to the disk device, /dev/vg1/vol1.

My write performance has an odd behavior.
If after booting I write to the volume I get roughly 175MB/sec. If after booting I do a mke2fs on the volume, mount it, umount it, then write to the volume I get roughly 230 MB/sec.

Any ideas? How can I get top speed without first mounting then umounting the volume?
By the way, I tried binding a raw device to the lv and got very bad performance; around 80 MB/sec. Would that be expected?

(I'm using redhat 9.0 -> lvm-1.0.3-12)

Quoted 33 lines
Quoted 8 lines

Thanks...

_______________________________________________
linux-lvm mailing list
[email protected]
http://lists.sistina.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

Signature · 22 lines
Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
     Nevertheless it needs not so stupid people to solve them ***

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                   56242 Marienrachdorf
                                                   Germany
[email protected]                           +49 2626 141200
                                                        FAX 924446
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-


_______________________________________________
linux-lvm mailing list
[email protected]
http://lists.sistina.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

*** Software bugs are stupid.
Nevertheless it needs not so stupid people to solve them ***

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen Sistina Software Inc.
Senior Consultant/Developer Am Sonnenhang 11
56242 Marienrachdorf Germany
[email protected] +49 2626 141200

                                                       FAX 924446

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-