Yes, Arkeia claims it's using 1.2 compression (with LZ1 I think). What
sort of compression could I use with tar to achieve similar results to
Arkeia? I tried compress & gzip and it went just as slow
What's the switch to play with the blocking factor?
Also, I tried setting the block size to 2048 to see if it speeds it up
and it didn't help at all..
It's an Ecrix VXA-1 Tape Drive on a Adaptec 2940 SCSI Card.
>From dmesg:
scsi0 : Adaptec AIC7XXX EISA/VLB/PCI SCSI HBA DRIVER, Rev 6.2.4
<Adaptec 2940 SCSI adapter>
aic7870: Single Channel A, SCSI Id=7, 16/253 SCBs
Vendor: ECRIX Model: VXA-1 Rev: 2848
Type: Sequential-Access ANSI SCSI revision: 02
(scsi0:A:4): 10.000MB/s transfers (10.000MHz, offset 15)
st: Version 20011103, bufsize 32768, wrt 30720, max init. bufs 4, s/g
segs 16
Attached scsi tape st0 at scsi0, channel 0, id 4, lun 0
Arkeia *is* doing a full backup.
I'll give ctar a go. Maybe tar can't compress as well as Arkeia can?
Thanks again Matt.
On Wed, 2002-04-10 at 10:47, Matt Hyne wrote:
>
> If Arkeia is backing up at 180Mb/min then this is equivalent to 3Mb/s, 2-3x
> faster than tar.
>
> Is Arkeia using compression ??? It is possible, and that may be why it is
> reporting faster transfer times to tape than tar is.
>
> You can also play with the tar blocking factor - it will depend on the
> network transfer speed.
>
> The other thing is, what sort of tape drive are you using, what sort of
> controller ? What is the maximum rated transfer rate for the tape drive ?
>
> Another stupid question - is Arkeia doing a FULL backup or an incremental ?
>
> From the look of this, you network is probably not the bottleneck. I
> would also suggest you take a look at ctar (do a google search). It costs
> money but you can install a trial version and compare that.
>
> Matt
>
> At Wednesday, 10-04-02 09:43 (+1000), Gonzalo Servat wrote:
> >Hi Matt
> >
> >I took your advice and tried backing up / on the backup server
> >(excluding /dev and /proc of course) to tape and tar reported:
> >
> >Total bytes written: 1427005440 (1.3GB, 1.2MB/s)
> >
> >It took about 15 minutes to complete this. My fileserver has about 30GB
> >worth of data. So, it would take approximately 6 hours to complete using
> >tar. This is just for the fileserver. It's actually taking a lot longer
> >than 6 hours (since it has to come over through the network) but
> >anyway... using Arkeia, I can backup the fileserver AND mail server
> >(which is only an extra 3 or so gigs) in 2 hours and 20 minutes. Arkeia
> >reports the speed was 180MB/min.
> >
> >There's something I'm doing wrong here and Arkeia is doing right because
> >I don't understand how Arkeia can backup ~160 faster than tar.
> >
> >Any further ideas??
> >
> >
> >
> >On Tue, 2002-04-09 at 17:56, Matt Hyne wrote:
> > >
> > > Generally, tapes are streaming, so it is possible that if the transfer
> > rate
> > > across the network is slow then more tape may be required for the same
> > > amount of data.
> > >
> > > Really - you need to determine the bottleneck - can you tar from one
> > > machine to the HDD on another and see how long it takes - and then locally
> > > tar this data to the tape drive. That should give you some good ideas of
> > > where the performance bottleneck is.
> > >
> > > At Tuesday, 09-04-02 16:42 (+1000), Gonzalo Servat wrote:
> > > >Hi All
> > > >
> > > >I was performing backups across the network using Arkeia until one day
> > > >the wrong tape was inserted and the whole tape cycle went haywire (as it
> > > >requires you enter the right tape with the right label or you get a nice
> > > >email in the morning asking you to insert the right tape - when infact,
> > > >I DID enter the right tape) and so I got pretty p@#@ed off at Arkeia and
> > > >decided to switch to using tar (as I can insert any tape and it will
> > > >write, plus tar is pretty universal accross *nix systems so I can
> > > >restore on any system)
> > > >
> > > >Aaaanyway, the point of my story is... it would normally take ~2.5hours
> > > >to backup 33GB across the network using Arkeia to tape.
> > > >With tar, it takes over 8 hours at which point it gives me a nice "no
> > > >space left on device" message on the screen.
> > > >
> > > >I'm not using gzip compression. I've tried this and it doesn't help the
> > > >speed problem (or capacity problem)
> > > >
> > > >The backup unit is an Ecrix VXA-1 using V17 tapes.
> > > >
> > > >Any ideas??
> > > >
> > > >Thanks in advance!
> > > >
> > > >Regards,
> > > >
> > > >Gonzalo.
> > > >
> > > >
> > > >--
> > > >SLUG - Sydney Linux User Group Mailing List - http://slug.org.au/
> > > >More Info: http://lists.slug.org.au/listinfo/slug
> > >
> > >
> > > --
> > > SLUG - Sydney Linux User Group Mailing List - http://slug.org.au/
> > > More Info: http://lists.slug.org.au/listinfo/slug
>
>
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