Date: Fri, 18 May 2007 16:10:45 -0700 (PDT) From: mjacob@freebsd.org To: freebsd-scsi@freebsd.org Cc: freebsd-performance@freebsd.org Subject: Dell/Perc5 raid/MPT SAS Integrated Raid Write Performance Message-ID: <20070518153412.C75640@ns1.feral.com>
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A lot of users have seen some very poor write performance on the MPT (LSI-Logic) driven SAS/SATA controllers, particularly those that function in Integrated Raid (mirroring) mode. Some of the reported performance issues are pretty clearly single spindle small transfer IOPS issues. For example, directory intensive and small file operations like mail server applications can do very poorly on single spindle SATA drives that are connected via a SAS channel that doesn't enable write cacheing on the SATA drive (i.e., does not flow through WCE for SCSI emulation, as the LSI-Logic *apparently* does not). Benchmarks like Postmark show pretty amazing differences when run on a PATA or native SATA based drive (1000s of ops/second) and on single Fibre Channel or SCSI drives (100s of ops/second) and can be even worse for SATA drives on a SAS controller. In these cases, there isn't much to be done- the h/w being picked doesn't match the application. However, other users have reported things which are *clearly* bad performance issues. In these cases users have reported sequential write speed to be a small fraction of read speed. That is, a single threaded read of a 10GB file will get spindle rotational speed magnitude for the disk in question (~40MB/s) but will only write at around ~6MB/s. This is clearly broken and wrong. Since I don't actually have a *lot* of MPT h/w and none that shows this write performance problem could folks do me a favor and at the next reboot get into the LSI-Logic BIOS utilities and find me all the firmware revision numbers? This might help me nail down some differences to go talk to LSI-Logic about. The overriding LSI-Logic BIOS revision is of interest, but also any of the firmware revision numbers. For example, the loaned Sunfire 4100 I have has 6.0.2.0 for the BIOS revision, but 1.04.00.00-IR for the firmware- and this system, which has two integral SAS 2.5" drives, writes at 50MB/s with them set up as an integrated mirror. -matt
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