You said it yourself: RAID. Not magic, it is only writing on multiple disks in 
parallel.

The disks I have in my NAS are WD Reds, rated at 112 MB/s and performance 
tested (by Tom's Hardware) to write at speeds from about 70 MB/s (center of the 
disk) to about 150 MB/s (outside).

I've seen much higher speeds in my NAS, where they are configured in a 12 drive 
array with 2 parity disks.
The NAS has two 1 GB network interfaces bonded together to 2 Gbit. That 
translates to roughly 250 MB/s, but the network is *still* more of a bottleneck 
than the disks.

The disks only become the deciding factor when there's a lot of non-sequential 
access (many people using it at the same time, plus it's also doubling as the 
iSCSI store for a few less important VMWare virtual machines).



-----Original Message-----
From: Dimitri Maziuk [mailto:dmaziuk AT bmrb.wisc DOT edu] 
Sent: 19 May 2015 19:43
To: bacula-users AT lists.sourceforge DOT net
Subject: Re: [Bacula-users] Is Bacula and a LTO drive right for me?

On 05/19/2015 11:42 AM, Bryn Hughes wrote:
...
> recent LTO versions (5/6) you really need to make sure your disk setup 
> on your backup storage server is capable of keeping up with the tape 
> drive - most consumer hard drives top out at about 120MB/sec for 
> sequential reads and much less than that for random I/O (such as having 
> backup jobs writing to the disk at the same time as the tape drive is 
> reading from it)

Wow these seagate nas drives must be magic then: it's 120MB/s sequential
read yet I get consistent 340MB/s sustained writes

> 11-May 23:00 starfish-sd JobId 13: Despooling elapsed time = 00:02:24, 
> Transfer rate = 345.8 M Bytes/second
...
> 12-May 12:30 starfish-sd JobId 13: Despooling elapsed time = 00:02:25, 
> Transfer rate = 343.4 M Bytes/second
...
> 14-May 03:33 starfish-sd JobId 34: Despooling elapsed time = 00:02:27, 
> Transfer rate = 338.8 M Bytes/second
...
> 18-May 19:49 starfish-sd JobId 57: Despooling elapsed time = 00:02:26, 
> Transfer rate = 341.1 M Bytes/second

and so on. On software raid-5-ish (raidz1) with lz4 compression at
filesystem level.

How about you iostat that LTO 5/6 drive while a restore job is reading
from it and a backup job is writing at the same time and then post speed
comparisons?

-- 
Dimitri Maziuk
Programmer/sysadmin
BioMagResBank, UW-Madison -- http://www.bmrb.wisc.edu

------------------------------------------------------------------------------
One dashboard for servers and applications across Physical-Virtual-Cloud 
Widest out-of-the-box monitoring support with 50+ applications
Performance metrics, stats and reports that give you Actionable Insights
Deep dive visibility with transaction tracing using APM Insight.
http://ad.doubleclick.net/ddm/clk/290420510;117567292;y
_______________________________________________
Bacula-users mailing list
Bacula-users AT lists.sourceforge DOT net
https://lists.sourceforge.net/lists/listinfo/bacula-users