Date: Thu, 26 Feb 2009 08:08:42 -0600 From: Josh Paetzel <josh@tcbug.org> To: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl> Cc: questions@freebsd.org Subject: Re: SAS drives seem slow Message-ID: <521399F6-5C55-4ECD-8DC7-46DC7432F250@tcbug.org> In-Reply-To: <alpine.BSF.2.00.0902260728040.12252@wojtek.tensor.gdynia.pl> References: <F1AB5657-660C-4554-BCF5-9E5C8001C74D@tcbug.org> <alpine.BSF.2.00.0902260728040.12252@wojtek.tensor.gdynia.pl>
next in thread | previous in thread | raw e-mail | index | archive | help
On Feb 26, 2009, at 12:28 AM, Wojciech Puchar wrote: >> FreeBSD services.tcbug.org 8.0-CURRENT FreeBSD 8.0-CURRENT #0: Mon >> Feb 16 21:07:14 UTC 2009 root@:/usr/obj/usr/src/sys/SERVICES >> amd64 >> >> But 6.x and 7.x give similar results. >> >> The disks themselves are capable of sequential read/write in the >> 180 Meg/sec range, so I'm trying to understand why I'm being told >> they are 100 Meg/sec, and why that seems to be their real world >> performance cap. >> > > probably you use RAID5 Hrmm, I should have included drive configuration. root@services /home/jpaetzel ->tw_cli /c0 show Unit UnitType Status %RCmpl %V/I/M Stripe Size(GB) Cache AVrfy ------------------------------------------------------------------------------ u0 RAID-1 OK - - - 135.031 ON ON u1 RAID-1 OK - - - 298.013 ON ON VPort Status Unit Size Type Phy Encl-Slot Model ------------------------------------------------------------------------------ p0 OK u0 136.98 GB SAS 0 - FUJITSU MBA3147RC p1 OK u0 136.98 GB SAS 1 - FUJITSU MBA3147RC p2 OK u1 298.09 GB SATA 2 - WDC WD3200AAKS-00SB p3 OK u1 298.09 GB SATA 3 - WDC WD3200AAKS-00SB But I get similar results when I connect just a single SAS drive and export it as a raw device. It's also worth noting that the SATA drive array is reported as 100MB/sec transfers, even though the drives aren't capable of anything close to that, unless they are reading from cache, in which case SATA2 is capable of more like 300MB/sec...but then so is SAS... Thanks, Josh Paetzel
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?521399F6-5C55-4ECD-8DC7-46DC7432F250>