[Networker] NetWorker compressasm and adv_file devices

2008-05-30 10:56:56
Subject: [Networker] NetWorker compressasm and adv_file devices
From: Rich Graves <rgraves AT CARLETON DOT EDU>
Date: Fri, 30 May 2008 09:51:23 -0500
There's a lot of past discussion of the pros and (predominantly) cons of 
turning on the NetWorker client compression directives when your tape devices 
that do their own compression. But what about adv_file devices?

It looks like a multiple win. I probably speed up network I/O a little bit. I 
probably speed up writes to the adv_file volumes on my storage node. I probably 
extend the lifetime of my tier3/10TB Disk Option license -- upgrading to 
tier4/50TB would cost me $20K plus support (is this true? never having actually 
exceeded my licensed disk backup option limit, though i'm starting to get 
close, how exactly does NetWorker verify compliance?). I probably slow down 
clones from disk to tape somewhat, but it looks like I am still able to feed my 
new LTO-4 drives at 80+ MBps without shoe-shining.

Background: Our 7.2->7.4.2 Upgrade Success Story

Old system
NetWorker 7.2.2 on RHEL 3 32-bit. Backups went to Apple XServe RAIDs (best 
price/gigabyte for FC-to-SATA storage 2 years ago; this has since changed) at a 
DR site on the other end of a 5km LH fibre channel link, and were then cloned 
back to an Overland NEO library with 4 SDLT-320 drives. 

Pressure to upgrade
The 49 tapes in the SDLT-320 library were only enough for about 7 days' worth 
of backups. Frequent swapping of tapes was tedious and error-prone. As much as 
I was offended by the elimination of nwadmin and introduction of Java GUI, it 
was time for RHEL3 and NetWorker 7.2.2 to go.

New system
NetWorker 7.4.2 32-bit version (not 64-bit, due to NetWorker issue LGTsc06585) 
on RHEL 5.2 64-bit. SELinux is enabled, with the default targeted policy in 
Enforcing mode -- no issues thus far. It is also running a Xen kernel, with 
NetWorker in the master Dom0 -- no issues thus far. My NetWorker server can 
host Xen guests in a DR situation, or possibly (with live DomU migration) 
during the normal business day, when the system is otherwise idle. Same 
strategy of primary backups to remote XServe RAIDs with cloning to a tape 
library elsewhere, but the tape library is now a Dell TL4000 with 2 FC-attached 
LTO-4 drives. I bought FC rather than SAS because it saved me a PCIe slot 
(dual-port HBA, one port connects to disks and one port connects to tapes) and 
allows me to locate the tape library more than 4m away. Although LTO-3 would 
have met our needs for at least three years, I bought LTO-4 because the cost 
differential wasn't that great and (unlike the case with SDLT) I have heard!
  from multiple sources that LTO-4 can speed-match just as slow as LTO-3, so 
why not.
Rich Graves Sr UNIX and Security Admin
CMC135: 507-646-7079 Cell: 952-292-6529

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