Date: Sun, 4 Feb 2001 12:41:49 -0800 (PST) From: Tom Samplonius <tom@sdf.com> To: freebsd-scsi@freebsd.org Subject: Tags and the mly driver Message-ID: <Pine.BSF.4.05.10102041234140.11446-100000@misery.sdf.com>
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According to camcontrol, SCSI disks attached via the mly driver are not using tagged command queuing by default. I've been investigating why the performance of the a Mylex AccelRAID 352 (mly driver) was about 30 to 40% slower than an older Mylex AccelRAID 250 (mlx driver). mly uses the CAM layer, and mlx does not. Performance was measured with postmark using 10,000 files, and 50,000 transactions. Anyhow, attempts to raise the number of tags via camcontrol via seems to work (camcontrol tags da0 -N 4), however shortly after increasing it to 16, the entire disk array hung. Are tags just unsupported on drivers that provide a virtualized SCSI interface like the mly driver? Or are there driver and/or hardware limitations that prevent them working? Tom To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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