On Tue, 12 Jun 2007 14:14:56 -0700, Ross Boylan said:
The Berkeley Database apparently requires that hot backups read disk
pages atomically. They note that most system cp commands do so; I've
searched the manual, FAQ, and newsgroups, but can't find how bacula
operates when reading a file.
Does anyone know if I can count on the reads taking whole pages?
Generally, no.
Specifically, possibly, at least if the page size is a factor of 65536, you
don't set sparse=yes, the OS guarantees that a call to read(2) with a page
aligned size will do it and also the network allows it. In these cases, it
looks like the current read size equals the network buffer size (see Maximum
Network Buffer Size).
You could try using strace to see what bacula-fd is doing in practice.
__Martin
Re: [Bacula-users] exabyte autochanger From: Maria McKinley
- 2007-06-13 21:47
Broderick Wood wrote:
I would also do a quick check to make sure you have LUN support enabled.
What is LUN support, and how do I check to make sure it is enabled?
~maria
On Wed, 13 Jun 2007 14:24:09 -0700
Michael Nelson <mnelson < at > in...> wrote:
Are you sure that /dev/sg0 is in fact the autochanger device and not the
tape drive?
For instance on my server (from dmesg output):
(scsi3:A:4): 160.000MB/s transfers (80.000MHz DT, offset 127, 16bit)
Vendor: CERTANCE Model: ULTRIUM 3 Rev: 1856
Type: Sequential-Access ANSI SCSI revision: 04
Attached scsi generic sg2 at scsi3, channel 0, id 4, lun 0, type 1
st: Version 20040403, fixed bufsize 32768, s/g segs 256
Attached scsi tape st0 at scsi3, channel 0, id 4, lun 0
st0: try direct i/o: yes (alignment 512 B), max page reachable by HBA
134217727
Vendor: QUANTUM Model: UHDL Rev: 0031
Type: Medium Changer ANSI SCSI revision: 02
Attached scsi generic sg3 at scsi3, channel 0, id 4, lun 1, type 8
So the generic device for my tape drive is /dev/sg2 (but the tape drive
is normally addressed as /dev/nst0) and the changer for it is /dev/sg3.
It would be interesting to see the output of "cat /proc/scsi/scsi" on
your machine.
[root < at > nts ~]# cat /proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
Vendor: LSILOGIC Model: 1030 IM Rev: 1000
Type: Direct-Access ANSI SCSI revision: 02
Host: scsi0 Channel: 00 Id: 08 Lun: 00
Vendor: IBM Model: 25P3495a S320 1 Rev: 1
Type: Processor ANSI SCSI revision: 02
Host: scsi3 Channel: 00 Id: 04 Lun: 00
Vendor: CERTANCE Model: ULTRIUM 3 Rev: 1856
Type: Sequential-Access ANSI SCSI revision: 04
Host: scsi3 Channel: 00 Id: 04 Lun: 01
Vendor: QUANTUM Model: UHDL Rev: 0031
Type: Medium Changer ANSI SCSI revision: 02
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