Date: Wed, 21 May 2008 14:30:51 -0500 From: Chris Dillon <cdillon@wolves.k12.mo.us> To: Scott Long <scottl@samsco.org> Cc: freebsd-scsi@freebsd.org Subject: Re: Very poor performance from Dell/LSI Logic SAS 3000 series SATA/SAS RAID controller FreeBSD 6.3 Message-ID: <20080521143051.17771kseoxrlhy7f@www.wolves.k12.mo.us> In-Reply-To: <48336EA0.3050109@samsco.org> References: <4832C397.3090004@calorieking.com> <4832E0EE.3030402@samsco.org> <4832E6C2.7040205@calorieking.com> <48336EA0.3050109@samsco.org>
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Quoting Scott Long <scottl@samsco.org>: > For data reliability, you really don't want it enabled by default. The > problem is that SATA/ATA performs so poorly without it that everyone > turns it on and lives with the consequences. The tweak that I > recommended puts it in line with what the FreeBSD ATA driver has been > doing for years. Doesn't SATA NCQ solve this particular performance vs. reliability =20 problem since it safely allows multiple outstanding write requests? =20 Of course that means the SATA RAID controller would have to use NCQ on =20 the drives and would probably also need its own non-volatile cache. =20 I've always assumed this is how SCSI/SAS drives (with TCQ) perform as =20 well as they do without sacrificing data integrity. We recently bought a new HP DL380G5 server with a P800 SAS RAID =20 controller, MSA60 external drive shelf with 12 750GB SATA drives, =20 11-drive RAID5 array w/ hot-spare (a few too many drives in a single =20 RAID5 array, I know, but I'm experimenting). The system is running =20 Windows Server 2K3 R2. Without telling the P800 to enable the SATA WC =20 (it has an option to do so, off by default), when doing a drag and =20 drop file copy of several very large files from the internal SAS array =20 to the external SATA array it writes 300MB/sec. I briefly enabled the =20 "Physical Drive Write Cache" on the controller just a few minutes ago =20 and ran another test and didn't notice any difference in write speed. =20 I can only assume from this that the P800 is using NCQ on the SATA =20 drives. --=20 Chris Dillon - NetEng/SysAdm Reeds Spring R-IV School District Technology Department 175 Elementary Rd. Reeds Spring, MO 65737 Voice: 417-272-8266 Fax: 417-272-0015
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