[Samba] Gigabit Throughput too low

Duncan, Brian M. brian.duncan at kattenlaw.com
Fri May 13 20:11:00 GMT 2005

Oops.. did not realize I was responding on the list before. Excuse me, I
am not even sure this belongs here.

I know I would increase my possible rates going raid, I am using JFS
BTW. This is not a production box in a company.
Its actually my video server at home, that normally has 1 or 2 clients
hitting it at a time. (I need (or want) max bandwidth at those times)

What I am trying to obtain is speed across the wire - comparable to what
I can get copying from 1 drive on 1 channel to another drive on another
channel from the server (through the whole transfer) over the wire Which
I currently cannot obtain.)

If I can currently take a 4 gig file on drive 1 controller one, and copy
it to drive 1 on controller 2 at a constant 20 Megabytes per second
locally.  You would think I should be able to copy a file from the 1
Gigabit network to drive 1 controller 2 at at least the same speed? (The
client is capable of delivering the file at the speed)

I am just trying to figure out in my Linux config what exactly is
causing this bottleneck for me.  I don't know if it's Samba, I am
starting to think it's a caching issue. (Dirty cache)

BTW thanks everyone for the feedback.

-----Original Message-----
From: Greg Freemyer [mailto:greg.freemyer at gmail.com]
Sent: Friday, May 13, 2005 2:53 PM
To: Duncan, Brian M.
Cc: Paul Griffith; samba at lists.samba.org
Subject: Re: [Samba] Gigabit Throughput too low

On 5/13/05, Duncan, Brian M. <brian.duncan at kattenlaw.com> wrote:
> 512 Megs of ram in server
> Pentium 4 2.0 Ghz
> 2 Ultra 133 controllers - 8 drives total - all 300 gig drives running
> at max UDMA support with write back cache turned off on each drive.
> (Clients connected are all at 1 Gig full duplex)
> FC2, with Samba 3.0.10-1
> Any tweaks I try I test before and after and have only left in place
> what tweaks seemed to improve performance.
> I am just running into a wall with Linux's manner that it handles
> caching of the files I think before it writes them to disk.  I have
> seen my transfers start out as high as 50 Megabytes per second, but
> then they slowly go down (seen it go as low as 1 Megabyte per sec) My
> guess is if I added more memory to the server that time for it to slow

> down would be increased a bit. (I was going to confirm that this
> weekend)

You do know that 10 MB/sec is not horrible for what you describe above.

ie. You have a very low cost ide-controller structure.  You have
multiple drives per ide channel (in use at the same time?  I hope not
due to master/slave contention).

You don't describe any raid.  raid-10 is typically the fastest way to
go, but uses more drives.  A good 8-drive raid-10 is theoretically 4x
faster than no raid on writes and 8x faster on reads.  (Admittedly, that
is only in theory, but it should still be faster.)

You don't mention the filesystem, but I'm guessing ext3, which is also
not a great speed daemon.  I'm guessing you have the default journaling
setup.  Asssuming a journalling FS, you want to put the journal on some
dedicated spindles, not the same drives as the FS.

Basically, I would optimize your disk-subsystem speed before I started
worrying about your 1Gb/sec. LAN.

Personally, I would consider 3ware parallel IDE controllers, raid 5 at a
minimum (raid 10 if you can), xfs filesystem, dedicated journal drive.

3ware has a white-paper describing a high-performance Linux setup.
You might want to look at it.

With a $1000 3ware controller and lots of reconfiguration, you can
probably get your disk sub-system up to 100MB/sec with no probem.
Even 200 or 300 should be achievable.

Greg Freemyer
The Norcross Group
Forensics for the 21st Century


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