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List: amanda-users
Subject: Re: Backup NAS to LTO7 tape library
From: Greg Dickie <greg () justaguy ! ca>
Date: 2017-07-01 15:50:39
Message-ID: CAMwn2afM261yy=XPB3xUVxnuQUr95hy6k_yDa2OvrMStEk8X2Q () mail ! gmail ! com
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Hi Jon,
Thanks for the detailed response. It seems like specifically disabling
software compression has helped quite a bit.
Greg
On Sat, Jul 1, 2017 at 3:49 AM, Jon LaBadie <jon@jgcomp.com> wrote:
> On Fri, Jun 30, 2017 at 06:47:57PM -0400, Greg Dickie wrote:
> > Hi Jon,
> >
> > I did. I gave me this:
> > define tapetype IBM-LTO7 {
> > comment "Created by amtapetype; compression disabled"
> > length 5876531200 kbytes
> > filemark 4964 kbytes
> > speed 291436 kps
> > blocksize 2048 kbytes
> > }
> >
> > The drive is SAS connected on a 6G HBA. I'm not sure what units kps is.
> >
>
> KiloBytes / Second
>
> So you are able to feed the drive from memory at 290 MB/s,
> close to its rates 300.
>
> Of course, during a backup without a holding disk, you may
> lose speed in reading from disk, transferring over the network,
> etc.
>
> LTO drives are designed to stream (run at a constant speed).
> Typically they can stream at two speeds, maximum (300MB/s
> in your case) and half-maximum. The drives contain considerable
> memory to buffer the data feed which could vary in rate or be
> insufficient to maintain streaming.
>
> When the data feed is insufficient, the drive waits for the
> buffer to fill to some level, starts the tape, when up to
> speed writes from the buffer until it drops to some level.
> The drive stops writing, slows the tape to a stop, reverses
> the tape to before where it last wrote and stops. When the
> buffer fills again, this cycle of start/write/stop/reverse
> repeats. This undesireable behavior is called "shoe-shining".
> One result is very low write speeds.
>
> While a holding disk is not appropriate in all cases one
> purpose of a holding disk is to provide a consistant,
> high speed data source for feeding the tape drive.
>
> Jon
> >
> > On Fri, Jun 30, 2017 at 5:18 PM, Jon LaBadie <jon@jgcomp.com> wrote:
> >
> > > On Fri, Jun 30, 2017 at 03:30:19PM -0400, Greg Dickie wrote:
> > > > Hi Alan,
> > > >
> > > > Thanks for the response. It looks to me like taper is slow. I'm
> trying
> > > to
> > > > not use a holding disk, the NAS is 250TB and doesn't make sense to
> have
> > > > 250TB locally to cache it. It's connected by a 10G ethernet
> connection
> > > so I
> > > > "should" be able to stream pretty quickly from it. i did put a 1TB
> disk
> > > as
> > > > a part cache but that seemed to behave the same way.
> > > >
> > > Have you run amtapetype to see what speed
> > > you might expect as a maximum?
> > >
> > > Admins have often had great difficulty getting
> > > LTO drives to run at rated speed.
> > >
> > > jl
> > > --
> > > Jon H. LaBadie jon@jgcomp.com
> > > 11226 South Shore Rd. (703) 787-0688 (H)
> > > Reston, VA 20190 (703) 935-6720 (C)
> > >
> >
> >
> >
> > --
> >
> >
> > Greg Dickie
> > just a guy
> > 514-983-5400
> >>> End of included message <<<
>
> --
> Jon H. LaBadie jon@jgcomp.com
> 11226 South Shore Rd. (703) 787-0688 (H)
> Reston, VA 20190 (703) 935-6720 (C)
>
--
Greg Dickie
just a guy
514-983-5400
[Attachment #3 (text/html)]
<div dir="ltr">Hi Jon,<div><br></div><div> Thanks for the detailed response. It \
seems like specifically disabling software compression has helped quite a \
bit.</div><div><br></div><div>Greg</div></div><div class="gmail_extra"><br><div \
class="gmail_quote">On Sat, Jul 1, 2017 at 3:49 AM, Jon LaBadie <span \
dir="ltr"><<a href="mailto:jon@jgcomp.com" \
target="_blank">jon@jgcomp.com</a>></span> wrote:<br><blockquote \
class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex"><span class="">On Fri, Jun 30, 2017 at 06:47:57PM -0400, Greg \
Dickie wrote:<br> > Hi Jon,<br>
><br>
> I did. I gave me this:<br>
> define tapetype IBM-LTO7 {<br>
> comment "Created by amtapetype; compression disabled"<br>
> length <a href="tel:5876531200" value="+15876531200">5876531200</a> \
kbytes<br> > filemark 4964 kbytes<br>
> speed 291436 kps<br>
> blocksize 2048 kbytes<br>
> }<br>
><br>
> The drive is SAS connected on a 6G HBA. I'm not sure what units kps is.<br>
><br>
<br>
</span>KiloBytes / Second<br>
<br>
So you are able to feed the drive from memory at 290 MB/s,<br>
close to its rates 300.<br>
<br>
Of course, during a backup without a holding disk, you may<br>
lose speed in reading from disk, transferring over the network,<br>
etc.<br>
<br>
LTO drives are designed to stream (run at a constant speed).<br>
Typically they can stream at two speeds, maximum (300MB/s<br>
in your case) and half-maximum. The drives contain considerable<br>
memory to buffer the data feed which could vary in rate or be<br>
insufficient to maintain streaming.<br>
<br>
When the data feed is insufficient, the drive waits for the<br>
buffer to fill to some level, starts the tape, when up to<br>
speed writes from the buffer until it drops to some level.<br>
The drive stops writing, slows the tape to a stop, reverses<br>
the tape to before where it last wrote and stops. When the<br>
buffer fills again, this cycle of start/write/stop/reverse<br>
repeats. This undesireable behavior is called "shoe-shining".<br>
One result is very low write speeds.<br>
<br>
While a holding disk is not appropriate in all cases one<br>
purpose of a holding disk is to provide a consistant,<br>
high speed data source for feeding the tape drive.<br>
<br>
Jon<br>
<span class="">><br>
> On Fri, Jun 30, 2017 at 5:18 PM, Jon LaBadie <<a \
href="mailto:jon@jgcomp.com">jon@jgcomp.com</a>> wrote:<br> ><br>
> > On Fri, Jun 30, 2017 at 03:30:19PM -0400, Greg Dickie wrote:<br>
> > > Hi Alan,<br>
> > ><br>
> > > Thanks for the response. It looks to me like taper is slow. \
I'm trying<br> > > to<br>
> > > not use a holding disk, the NAS is 250TB and doesn't make sense to \
have<br> > > > 250TB locally to cache it. It's connected by a 10G \
ethernet connection<br> > > so I<br>
> > > "should" be able to stream pretty quickly from it. i did put \
a 1TB disk<br> > > as<br>
> > > a part cache but that seemed to behave the same way.<br>
> > ><br>
> > Have you run amtapetype to see what speed<br>
> > you might expect as a maximum?<br>
> ><br>
> > Admins have often had great difficulty getting<br>
> > LTO drives to run at rated speed.<br>
> ><br>
> > jl<br>
> > --<br>
> > Jon H. LaBadie <a \
href="mailto:jon@jgcomp.com">jon@jgcomp.com</a><br> > > 11226 South Shore Rd. \
<a href="tel:%28703%29%20787-0688" value="+17037870688">(703) 787-0688</a> (H)<br> \
> > Reston, VA 20190 <a href="tel:%28703%29%20935-6720" \
value="+17039356720">(703) 935-6720</a> (C)<br> > ><br>
><br>
><br>
><br>
> --<br>
><br>
><br>
</span><span class="">> Greg Dickie<br>
> just a guy<br>
> <a href="tel:514-983-5400" value="+15149835400">514-983-5400</a><br>
</span>>>> End of included message <<<<br>
<div class="HOEnZb"><div class="h5"><br>
--<br>
Jon H. LaBadie <a \
href="mailto:jon@jgcomp.com">jon@jgcomp.com</a><br> 11226 South Shore Rd. \
<a href="tel:%28703%29%20787-0688" value="+17037870688">(703) 787-0688</a> (H)<br> \
Reston, VA 20190 <a href="tel:%28703%29%20935-6720" \
value="+17039356720">(703) 935-6720</a> (C)<br> \
</div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br><div \
class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><img \
src="http://www.google.com/a/justaguy.ca/images/logo.gif"><br><br>Greg Dickie<br>just \
a guy</div><div>514-983-5400</div></div></div> </div>
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