FYI
I have 1Gb uplinks between bacula sd and client and get the following
results
Compression: NONE
Time: 07:16:58
Size: 831.14 GB
Files: 11,288,747
Speed: 32.46 MB/s
Compression: 0.00
Compression: LZO
Time: 07:56:38
Size: 653.04 GB
Files: 11,288,747
Speed: 23.38 MB/s
Compression: 0.21
Compression: GZIP
Time: 10:09:07
Size: 636.41 GB
Files: 11,288,747
Speed: 17.83 MB/s
Compression: 0.23
On Sat, Jun 27, 2015 at 4:19 PM, Alan Brown <a...@mssl.ucl.ac.uk> wrote:
> On 27/06/15 10:45, Dmitri Maziuk wrote:
>
> Compressing data on the client means fewer bytes to send over the wire.
> Block-level compression like bzip2 tends to be completely cpu-bound and
> anything bigger than a cellphone tends to have plenty of cycles to spare.
>
>
> Not entirely true and certainly not accurate for Gb/s and faster links.
>
> Individual CPU cores haven't changed much in terms of speed for nearly a
> decade and most compression algorithms are single threaded when fed from
> stdin (even pigz and pbzip). On top of that you're facing memory <-> CPU
> bottlenecks.
>
> The result when running gzip compression over a 1Gb/s link is that you'll
> usually achieve a maximum end-to-end rate of 30MB/s, vs the wire speed of
> 110MB/s ( b = bit, B=BYTE, aka o = octet if you're french )
>
> bzip is significantly worse. Even LZO gives little gain at 1Gb/s in
> exchange for making your CPU run hot and drawing more power than you need
> to.
>
> At 10Gb/s, LZO is a significant bottleneck.
>
>
> The takeaway: Unless you're backing up over a WAN (and a slow or
> overloaded one at that), wireside compression is not a net win.
>
> We have 300 people on our campus linking to the main site at 1Gb/s and
> whilst backing up machines on the main site to our satellite one we still
> achieve faster backups without compression than with it.
>
>
> The other side of compression is that it's a huge CPU drain. I already
> have enough problems with people rebooting windows systems mid-backup
> without adding even more incentive for them to hit the Big Red Button.
>
>
>
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network devices and physical & virtual servers, alerts via email & sms
for fault. Monitor 25 devices for free with no restriction. Download now
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