Date: Tue, 10 Apr 2007 22:04:17 +0200 From: Ivan Voras <ivoras@fer.hr> To: freebsd-hardware@freebsd.org Subject: Re: the performance of SAS is not better than SCSI in FreeBSD, WHY? Message-ID: <evgqk5$du4$1@sea.gmane.org> In-Reply-To: <224a745a0704092137h67f5f463w6b355535a6b8415f@mail.gmail.com> References: <224a745a0704092137h67f5f463w6b355535a6b8415f@mail.gmail.com>
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This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigAB8D48E3DDFE1E2317A08838 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Tzu-Hua Wang wrote: > Generally, the performace of SAS in FreeBSD is far worse than SCSI in > FreeBSD. > Is it normal? How can I do to improve the performance of SAS HD in Free= BSD? There's a huge number of possible reasons - unless you're testing the same controller (I think there exist SAS+SCSI controllers, I might be wrong), you can't conclude that the SAS interface is less supported. For what it's worth, I've got approximately the same numbers on DL380 G5, but I've attributed them to 2.5" small form factor drives. 2x 2.5" 10k RPM, CISS hw RAID1 2x 3.5", 7.5k RPM, soft RAID1 Full stroke 3.863 ms 5.942 ms Half stroke 3.929 ms 6.186 ms Quarter stroke 3.998 ms 5.700 ms Short forward 3.889 ms 4.060 ms Short backward 4.715 ms 4.748 ms Seqential outer 1.011 ms 0.167 ms Sequential inner 1.013 ms 0.177 ms Read transfer, outside 43.6 MB/s 61.2 MB/s Read transfer, middle 38.8 MB/s 54.8 MB/s Read transfer, inside 32.8 MB/s 34.9 MB/s The 3.5" drives were SATA in a different machine (Dell's). It might be that the CISS driver is unreasonably slow, which is kind of possible given the suspicious lower bound of about 1 ms in seeks. Maybe something is throttling the I/O rate? --------------enigAB8D48E3DDFE1E2317A08838 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.4 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGG+3BldnAQVacBcgRAqrwAKCaQKnetnrqmq6TRJMHwAoqEb9WmQCePcTd p4G/GDPCGq7N1BjZI0EBkdY= =HauS -----END PGP SIGNATURE----- --------------enigAB8D48E3DDFE1E2317A08838--
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