Re: [nslu2-linux] Maximizing Slug Fileserver Speed
- On Jul 2, 2006, at 3:28 AM, Attila Csipa wrote:
> On Sunday 02 July 2006 05:11, Brian Wood wrote:Good point. What you say is absolutely correct for drives being used
>> Is there a particular USB/IDE chipset(s) that gives the best
> What nobody seems to mention is the importance of the type of disks
> they are
> using. 2.5" disks are not 'just the same but smaller' than 3.5"
> disks. If you
> want to transfer large files, you will get noticeably lower speeds
> built-in disk cache won't help you and the lower spin rate of 2.5"
> really comes out in those cases (all this assuming that the USB2IDE
> can actually sustain that throughput). They are generally designed for
> notebooks (small size, lower power, more resistance to shock and
> heat, not
> top performance).
with their native (usually ATA) interface (although we are starting
to see some 7200 RPM 2.5" drives. I've also seen some 2GB and 4GB all
solid-state 2.5" drive replacements).
I guess I figured that the performance loss in going to the USB
interface was so great that it really didn't matter how fast the
drive was to start with.
Now I'm not so sure. I guess I'll just have to try using different
drives and see if there is a difference.
- On Jul 2, 2006, at 6:25 AM, Yann E. MORIN wrote:
> Brian,These are SD files recorded by a MythTV system using PVR capture
> On Sunday 02 July 2006 051, Brian Wood wrote:
>> The slug will serve MPEG-2 video files, mostly over 1GB in size.
> How many at the same time? Which bitrate: 4Mibps (SDTV) or >8Mibps
> What's between your slug and the player: WiFi, cat-5, PLT? One or
> more hub
> or switch? (see at bottom of mail).
cards. They are about 2.2GB per hour (more or less full D1). The
network is 100-base-T hard-wired (CAT-5E) with one switch, not
including the switch in the router.
>I should have said that my purpose is not to "play" the files, but to
>> I should use NFS and not Samba for maximum speed (not serving to
> To serve video (or music as well), why don't you use streaming?
> That would have the benefit of adding no file system overhead on
> the network, thus maximizing the bandwidth for the actual data
> (provided your storage medium can sustain the throughput).
give multiple machines access to the files in order edit them and
create DVD images to burn.
As such I don't think streaming would work, certainly not without
major changes to the editing software. Throughput is not an issue the
way it would be if playing, as there is no "real time" to keep up
with, but obviously the faster the server the less time spent waiting
>There had been a few posts here recently that seemed to indicate that
>> I should use a Big-Endian OS (not sure how much difference this might
>> From my experiments, that's not noticeable by timing with hardware,
> and even less noticeable for a human being. That said, if you need
> horsepower at the same time you transfer data, then you may loose
> a few ticks, but that's nothing compared to any context-switch.
a TCP/IP-intensive machine would be more efficient if running BE, but
I suspected the difference would be minor.
But I'm tending to run the BE OpenSlug in any case, certainly I don't
need the vast package library of the full Debian release just to run
an NFS server.
Unless, of course, somebody could convince me that OpenSlug is not
the best answer here.
>No NFS root, that would definitely not give me optimum speed. Just
>> I should De-underclock the slug (seems obvious).
> That should help, but again, serving video via streaming is mostly
> copy-from-disk-to-memory-to-network, and your limiting factors will
> probably be (in path-order):
> - disk-throughtput,
> - IDE2USB adapter,
> - USB throughput (you should be fine here!),
> - memory latency,
> - network throughput,
> rather than CPU performance
>> Should I use a hard drive or a flash device for the OS ? (I'm
>> assuming NFS would not give optimum speed).
> I don't get it right. Were your planing on an NFS-root? That
> is a bad idea to maximise your bandwidth usage!
> Anyway a hard drive for the rootfs would be better, you could even add
> some swap to help in those moments where you'd need it.
deciding between a hard drive and a flash device for root. I've never
tried a flash stick, always used drives with nice large swap partitions.
I've seen some "Fast Flash" NAND devices that are drop-in
replacements for 2.5" hard drives. They claim 17.7MB/sec. read/write
burst capability and 12MB sustained rates. Expensive, but look
awfully nice for a root filesystem, and plenty of room for swap.
Built-in "dynamic wear leveling", which I take to mean spreading out
the load so you don't wear out specific locations quickly.
>I think the first 3 you mentioned are the only simple choices for a
>> What filesystem should I use ?
> To store files, any _decent_ FS should do. ext2/3 or even reiserfs
> should be
> fine. Avoid FAT & co. and NTFS. Avoid any compressed FS (cramfs,
> JFFS2...) because those _are_ CPU-bound.
slug in any case. I know the Myth people go on endlessly about what
filesystem is best, usually with very conflicting results.
Anyway, much thanks for your input, it is appreciated.
- Apologies for not having found this earlier:
Some tests done with the copy of a 200MB file between a NSLU2 with
2.12-beta firmware and a Linux 2.8 (ubuntu), the test was performed
with the filesystem "mounted" and then a simple read/write of the
200MB via a python script.
nfs: 5.7MB/s 2.6MB/s
cifs: 3.5MB/s 1.9MB/s
samba: 2.2MB/s 1.85MB/s
nfs-server Version: 2.2beta47-2
Looks like we're all doing a bit better than that, but that may also
be with a 133Mhz. slug.