It depends, on a lot of factors.
You have to find the optimum setting that will work for you. Unfortunately
this depends on your clients, the type of data, the available bandwidth,
your server, the scsi bus, your tape drives, and the current moon phase.
There is no clear answer to your question.
Bye
Ernie
-----Original Message-----
From: Legato NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU]
On
Behalf Of William M. Fennell
Sent: Thursday, October 27, 2005 8:12 PM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: [Networker] Best usage of tape drives
Reducing the target sessions and server parallelism will decrease the
amount of time to
back up the data?
--------------------
William M. Fennell
UNIX Administrator
Channing Laboratory
Ernst Bokkelkamp wrote:
>Your message needs a bit of rewording:
>
>Our SERVER parallelism is at 40.
>Three tape devices are configured for 4 TARGET sessions and the other
>two are configured for two TARGET sessions each. If we are at
>generating 16 streams using all of our tape devices, parallelism will
>exceed the configured target session maximum and keep going up until 16
>sessions are running.
>
>Server parallelism: Max number of sessions a server has been configured
>to be active at the same time. Please note that the real limit depends
>on your license and the number of storage nodes that have been
>configured (see the manual!). Target setting: This is the number of
>sessions per tape drive before the next drive should be selected.
>However this is not a limit!
>
>Btw: You should target the minumum number of sessions to keep your
>drives spinning. It is bad practise to overload the drives with
>sessions, altough it doesn't make a difference it the only thing you do
>is backup and never intend to restore!. The reason for targetting the
>minimum number of sessions is easely explained: Just assume that you
>are backing up 16 clients with one saveset of 200 Gbyte each to 4
>drives, each with target sessions set to 4 and server parallelism set
>to 64. Running all sessions at the same time will cause each drive to
>hit the target level. Now if each client can generate sufficient
>bandwith to produce half the bandwith of a tape drive then you will
>need double the time for each client to backup all the data. But if you
>reduce the server parallelism (8) and target sessions (2) so that only
>half the clients can be active then each client will only use half the
>time and you can do all the backups in the same time. Does this make
>sense ?
>
>However, looking at restore, the target sessions can have very
>detrimental effect on the time needed. If you assume that the client is
>capable of taking up everything the tape drive can be delivered then
>the time to recover will depend on how fast the tape drive can move the
>tape (inches/second). Lets assume that the drive can move the tape,
>while reading, from beginning to end in 1 hour, then it will take one
>hour to read all the data on the tape. Now if one tape cartridge has a
>capacity to backup one client, then you will need n cartridges if n
>clients are backed up to the same tape drive with target sessions set
>to n and will run for n hours. This means that you will have to read n
>cartridges, or n x the tape length, using n hours to restore all the
>data on the client. This means that the restore of 1 (ONE) client will
>take n hours. This means the larger number of sessions to the drive
>then the longer it will take to read the tape, meaning the longer it
>will take to restore. For this reason it is wise to go for the minimum
>number of sessions to keep the drives spinning and to obtain an
>acceptable restore performance. This also means that if you don't care
>about restore then you can set the maximum number of sessions as you
>like.
>
>I hope this helps a bit to understand what can drive a networker backup
>administrator into insanity.
>
>Bye
>Ernie
>
>
>-----Original Message-----
>From: Legato NetWorker discussion
>[mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On Behalf Of William M. Fennell
>Sent: Wednesday, October 26, 2005 10:04 PM
>To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
>Subject: Re: [Networker] Best usage of tape drives
>
>
>Our parallelism is at 40.
>Three tape devices can take 4 target sessions and the other two can
>handle two each.
>Even if we are at 16 streams taking up all of our tape devices,
>parallelism will
>trump the target session limit and keep going up until 40 is reached. So I
>should expect to see 40 streams saving right?
>
>--------------------
>William M. Fennell
>UNIX Administrator
>Channing Laboratory
>
>
>
>Albert Eddie Contractor AFRPA/ESS wrote:
>
>
>
>>Archive Performance is kind of an itch to me that I am always trying
>>to
>>scratch.
>>
>>Speaking to Legato last week we discussed a strategy where I would
>>list
>>various specific directory trees to backup. Then you turn up
>>Parallelism allowing more data streams and voila this results in
>>multiple data streams per drive.
>>
>>Of course weighing in Backup data drive bandwidth ability, controller
>>bandwidth, LAN bandwidth and then the bandwidth ability of your
>>NetWorker components as well.
>>
>>(Does anyone else feel like they are tweaking VWs to race in the
>>sand?)
>>
>>The parallelism setup for the server (default 4 in NW7.1?) means that
>>if you don't have 5 data streams coming in, Networker is only going to
>>use ONE drive and leave the other drive for tape operations.
>>
>>If you lower your parallelism to 2 you should see the second drive
>>join
>>in when the third data stream is identified. I hope this helps.
>>
>>Semper Fidelis, /ALE
>>
>>Eddie Albert, Network Serf
>>Air Force Real Property Agency
>>Executive Services/Computer Systems
>>Desk (703) 696 - 5509 - Hip (703) 517-3855
>>Eddie.Albert AT afrpa.Pentagon.af DOT mil
>>
>>
>>
>>
>>
>>>-----Original Message-----
>>>From: Legato NetWorker discussion
>>>[mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On Behalf Of William M.
>>>Fennell
>>>Sent: Tuesday, October 25, 2005 4:41 PM
>>>To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
>>>Subject: [Networker] Best usage of tape drives
>>>
>>>Hi folks,
>>>
>>>I have a Server with three tape drives hooked up to it.
>>>I have a dedicated storage node with two tape drives hooked up to it.
>>>All drives are in a qualstar TLS-4000 and the tape drives are Sony
>>>700CDX AIT-3. We're running Solaris 8 on the Networker server and 9 on
>>>the storage node.
>>>We're at Networker 7.1.
>>>
>>>My storage node can of course only write local data to tape. My issue
>>>is that it only uses one drive! So it is trying to write 200+GB
>>>nightly from three file systems on this host to one tape. How can I
>>>make it use both tape drives? Currently it is taking about 8 hours to
>>>backup about 200GB nightly to one drive.
>>>I would like to improve on that performance.
>>>
>>>My two ideas are:
>>>1: reduce the number of target streams on each drive to two and then
>>>have one drive take two streams and the other take one stream.
>>>2: Maybe the drives need to be shared with each other?
>>>
>>>Many thanks,
>>>
>>>Bill
>>>
>>>To sign off this list, send email to listserv AT listserv.temple DOT edu and
>>>type "signoff networker" in the body of the email. Please write to
>>>networker-request AT listserv.temple DOT edu if you have any
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>>>http://listserv.temple.edu/archives/networker.html or via RSS
>>>at http://listserv.temple.edu/cgi-bin/wa?RSS&L=NETWORKER
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>
>To sign off this list, send email to listserv AT listserv.temple DOT edu and
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>
>To sign off this list, send email to listserv AT listserv.temple DOT edu and
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http://listserv.temple.edu/cgi-bin/wa?RSS&L=NETWORKER
>
>
To sign off this list, send email to listserv AT listserv.temple DOT edu and
type
"signoff networker" in the body of the email. Please write to
networker-request AT listserv.temple DOT edu if you have any problems wit this
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To sign off this list, send email to listserv AT listserv.temple DOT edu and
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