st buffer change - driver modification or boot param?

Issues related to hardware problems
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wkdpanda
Posts: 1
Joined: 2007/10/12 19:31:53

st buffer change - driver modification or boot param?

Post by wkdpanda » 2007/10/12 19:53:34

I have a box attached to a Scalar 1000 with 6 LTO-2 drives. The tape drives write with 256k block size for best performance. The default driver runs with a 32k block size. Should I change the parameters in the st module, or at boot time by adding a 'st=' line?

Anyone have any opinions or thoughts on these two methods?

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If I make the change in the module,
From the st.c file (/usr/src/linux/drivers/scsi)

module_param_named(buffer_kbs, buffer_kbs, int, 0);
MODULE_PARM_DESC(buffer_kbs, "Default driver buffer size for fixed block mode (KB; 32)");

If I change the line to:

module_param_named(buffer_kbs, buffer_kbs, int, 256);

Will this meet my needs?
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Changing at boot time would be doing something like the adding the following to the boot line in grub

st=buffer_kbs:256

Should I set the number of buffers or sg? Will the st driver use as many as needed if I don't?
max_buffers=xxx the maximum number of tape buffer set to xxx
max_sg_segs=xxx the maximum number of scatter/gather segments
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-Andrew

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