Date: Fri, 11 Mar 2005 18:58:47 -0500 From: "Dan Langille" <dan@langille.org> To: "Kenneth D. Merry" <ken@kdm.org> Cc: freebsd-scsi@freebsd.org Subject: Re: how does the scsi chain work? Message-ID: <4231EA67.15143.56AB2BB5@localhost> In-Reply-To: <20050311231347.GA43379@nargothrond.kdm.org> References: <4231D28B.28878.564DFBA1@localhost>
next in thread | previous in thread | raw e-mail | index | archive | help
On 11 Mar 2005 at 16:13, Kenneth D. Merry wrote: > On Fri, Mar 11, 2005 at 17:16:59 -0500, Dan Langille wrote: > > Hi folks, > > > > I added the following devices to my computer, all in one SCSI chain: > > > > sa0: <QUANTUM DLT7000 2561> Removable Sequential Access SCSI-2 device > > sa0: 20.000MB/s transfers (10.000MHz, offset 15, 16bit) > > sa1 at sym0 bus 0 target 6 lun 0 > > sa1: <QUANTUM DLT7000 2255> Removable Sequential Access SCSI-2 device > > sa1: 20.000MB/s transfers (10.000MHz, offset 15, 16bit) > > sa2 at sym0 bus 0 target 8 lun 0 > > sa2: <QUANTUM DLT8000 0114> Removable Sequential Access SCSI-2 device > > sa2: 20.000MB/s transfers (10.000MHz, offset 15, 16bit) > > > > Then I decided to do some concurrent testing. See below for details. > > The goal was really to test filling the tape. This exercises both > > the drive and the tape (all of which are used). > > > > Sometimes a single tar takes nearly 4 hours, sometimes it takes only > > 75 minutes. > > > > My question: It doesn't look like the load is shared evenly. Can > > someone talk a bit about this? That's a pretty general and wide > > question, I know... > > You might want to look at your media quality. You said that your drives > and media are used... > > In this case you even got a write error. That's pretty indicative of bad > media. (Or a drive that needs to be serviced I suppose.) But that's the tape filling up... surely? That's what the test does... fills the tape. Entirely. Usually, I see bad media with: Feb 15 07:06:53 lux kernel: (sa0:isp0:0:4:0): SPACE. CDB: 11 1 ff ff ff 0 Feb 15 07:06:53 lux kernel: (sa0:isp0:0:4:0): CAM Status: SCSI Status Error Feb 15 07:06:53 lux kernel: (sa0:isp0:0:4:0): SCSI Status: Check Condition Feb 15 07:06:53 lux kernel: (sa0:isp0:0:4:0): MEDIUM ERROR info:ffffffff csi:0,0,f,ba asc:11,0 Feb 15 07:06:53 lux kernel: (sa0:isp0:0:4:0): Unrecovered read error Feb 15 07:06:53 lux kernel: (sa0:isp0:0:4:0): Retries Exhausted Feb 15 07:06:53 lux kernel: (sa0:isp0:0:4:0): unable to backspace over one of double filemarks at end of tape Feb 15 07:06:53 lux kernel: (sa0:isp0:0:4:0): it is possible that this device needs a SA_QUIRK_1FM quirk set for it Feb 15 07:06:53 lux kernel: (sa0:isp0:0:4:0): tape is now frozen- use an OFFLINE, REWIND or MTEOM command to clear this state. > > [root@lux:/home/dan] # date && time tar cf /dev/nsa0 /usr && time > > tar cf /dev/nsa0 /usr && time tar cf /dev/nsa0 /usr && time tar c > > f /dev/nsa0 /usr && time tar cf /dev/nsa0 /usr && time tar cf > > /dev/nsa0 /usr ; date > > Thu Mar 10 22:31:57 EST 2005 > > tar: Removing leading '/' from member names > > > > real 75m15.394s > > user 0m45.666s > > sys 2m31.039s > > tar: Removing leading '/' from member names > > > > real 114m5.702s > > user 0m52.549s > > sys 2m45.939s > > tar: Removing leading '/' from member names > > > > real 156m18.091s > > user 0m51.538s > > sys 2m46.858s > > tar: Removing leading '/' from member names > > > > real 119m48.240s > > user 0m49.670s > > sys 2m45.721s > > tar: Removing leading '/' from member names > > tar: usr/home/bacula-restores/usr/X11R6/share/locale/bs/LC_MESSAGES: > > Write error > > > > real 195m0.408s > > user 0m38.779s > > sys 2m13.158s > > Fri Mar 11 09:32:26 EST 2005 > > > And you got another write error on this tape: > > > root@lux:/home/dan] # date && time tar cf /dev/nsa1 /usr && time tar > > cf /dev/nsa1 /usr && time tar cf /dev/nsa1 /usr && time tar cf > > /dev/n > > sa1 /usr && time tar cf /dev/nsa1 /usr && time tar cf /dev/nsa1 > > /usr ; date > > Thu Mar 10 22:53:40 EST 2005 > > tar: Removing leading '/' from member names > > > > real 103m35.344s > > user 0m50.394s > > sys 2m44.732s > > tar: Removing leading '/' from member names > > > > real 112m40.647s > > user 0m50.555s > > sys 2m46.049s > > tar: Removing leading '/' from member names > > > > real 152m45.638s > > user 0m52.656s > > sys 2m46.040s > > tar: Removing leading '/' from member names > > > > real 201m0.014s > > user 0m53.838s > > sys 2m51.051s > > tar: Removing leading '/' from member names > > tar: usr/home/bacula- > > restores/usr/src/contrib/ncurses/form/fld_link.c: Write error > > > > real 93m59.622s > > user 0m22.483s > > sys 1m8.356s > > Fri Mar 11 09:57:41 EST 2005 > > With a tape, if it can't write in one area, it'll skip down the tape to try > to find an area it can write to. So you may just be running into bad areas > on the tape. > > I would recommend buying some new media that is speced to work on those > drives, and then try it out. If you still have variable performance and > write errors, then you may have a drive problem. sa2 was writing to new media. > Don't forget to run a cleaning tape through if those drives use cleaning > tapes. Yep. I got to get me some of that. -- Dan Langille : http://www.langille.org/ BSDCan - The Technical BSD Conference - http://www.bsdcan.org/
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?4231EA67.15143.56AB2BB5>