From mboxrd@z Thu Jan 1 00:00:00 1970 From: Friedrich Lobenstock Subject: blocksize limitations in scsi tape driver (st) when used with DLT1 tape drives? Date: Thu, 05 Sep 2002 21:35:50 +0200 Sender: linux-kernel-owner@vger.kernel.org Message-ID: <3D77B216.8070205@fl.priv.at> Reply-To: Linux-SCSI Mailingliste Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Return-path: To: Linux-SCSI Mailingliste Cc: Linux-Kernel Mailingliste List-Id: linux-scsi@vger.kernel.org Hi! I'm having an odd problem here. I use SuSE Linux 8.0 with kernel 2.4.18-64GB-SMP, arkeia as backup software and a Tandberg VS80 (DLT1) streamer. After some trial and error I found out that I have to use a fixed block size for DLT streamers (same applies to LTO ones). This document, found at HP, tells you in details about which blocksize to use: http://www.hp.com/cposupport/information_storage/support_doc/lpg50167.html Now I told arkeia to use a blocksize of 65536, 32768 and 16384 and it could not write to the tape. All I got in the log was: Sep 4 22:04:50 filesrv kernel: st: Unloaded. Sep 4 22:08:40 filesrv kernel: st: Version 20020205, bufsize 32768, wrt 30720, max init. bufs 4, s/g segs 16 Sep 4 22:08:40 filesrv kernel: st0: Block limits 2 - 16777214 bytes. Sep 4 22:08:41 filesrv kernel: st0: Incorrect block size. Sep 4 22:08:45 filesrv kernel: st0: Write not multiple of tape block size. Sep 4 23:20:06 filesrv kernel: st: Unloaded. Sep 4 23:20:30 filesrv kernel: st: Version 20020205, bufsize 524288, wrt 522240, max init. bufs 16, s/g segs 64 Sep 4 23:20:30 filesrv kernel: st0: Block limits 2 - 16777214 bytes. Sep 4 23:20:33 filesrv kernel: st0: Incorrect block size. Sep 4 23:20:35 filesrv kernel: st0: Write not multiple of tape block size. (As you might have notice in the second case I'm loading st with buffer_kbs=512, max_buffers=16 and max_sg_segs=64 but that makes no difference compared to the default values) BUT now comes the cloo: at and below a blocksize of 8192 it was possible to write to the tape. At 1024 the backup slowed down from 20 min to 4 hours, but at 8192 the backup speed is normal (the later on with the st options you can see above, but haven't tested if that makes a difference). LTO drives in contrast to DLT drives are happy with a blocksize of 1024 and backup speed is normal at this blocksize. Everytime when arkeia could not write to the tape I checked with mt to display the blocksize and I verified that arkeia set it to the value I told it to. Now with arkeia set to a blocksize of 8192: filesrv:~ # mt -f /dev/st0 status drive type = Generic SCSI-2 tape drive status = 1073750016 sense key error = 0 residue count = 0 file number = 0 block number = 0 Tape block size 8192 bytes. Density code 0x40 (unknown). Soft error count since last status=0 General status bits on (41010000): BOT ONLINE IM_REP_EN I think there must be something wrong in the scsi tape driver(st). Can someone shine some light on this? PS: Reply-to set to linux-scsi. -- MfG / Regards Friedrich Lobenstock