External Storage & Bandwidth Considerations

[RickGG]

I have gotten in the practice in the last 2 years of using USB 2.0 to connect external storage to my workstations and fileservers. Performance has seemed adequate, and more than anything, the convenience of popping in a 300 GB has been great. I have gotten to the point where in addition to RAID 0, I am using USB 2.0 drives in the place of tape drives for nightly backup. Even serving up MP3 and MPG to my streaming media server off of an externally attached USB 2.0 drive hasn't produced any obvious problems.

In doing some research, I learned that there is a performance cost of doing USB 2.0 to PATA or SATA- obviously, this has been negligible, but I wanted to get some advice from the group regarding theoretical bandwidth of the various technologies that are involved.

Max Theoretical Bandwidth Assumptions (please correct if wrong):

LAN - 100Mbit/sec
USB 2.0 - 480 Mbits/sec
PATA 133 - 1064 Mbits/sec
SATA 300 - 2400 Mbits/sec

Question #1: If I want to mount storage on my network such that it is accessible via the LAN, does it really matter if I am using PATA or SATA since the performance bottleneck is always going to be the LAN (I know that Gigabit ethernet is available, but for now, I am not considering this)?

This brings me to my second question: In looking at some of these SOHO NAS devices, are there any advantages to buying one of these over putting together a cheap little file server with a 100 Mbit card from old parts?

Some examples (ranging from cheaper adapters, to NAS):
http://www.newegg.com/Product/Product.asp?Item=N82E16833127156
http://www.newegg.com/Product/Product.asp?Item=N82E16822106001
http://www.newegg.com/Product/Product.asp?Item=N82E16822155306



TIA,

Rick

 

[Madwand]

Interface speed specifications for PATA and SATA are pretty useless, as no available hard drives are able perform at that level. Even with SATA XIII let's say, with a googolplex bytes per second interface speed, the fastest current desktop drives will only be able to transfer at most around 80 MB/s sustained, more typically around 60 MB/s max, and around 30-45 MB/s average.

100Base-T will only do around 10 MB/s at best
USB2 somewhere around 40 MB/s at best
Gigabit somewhere around 60 MB/s at best; typically limited by drives on both sides, but also file transfer inefficiencies, etc.

Typical current consumer NAS boxes tend to perform poorly; even with gigabit ports, etc., these typically sustain not much more than 100Base-T speeds according to Tom's NAS benchmarks for example.

Building a well-performing DIY NAS box isn't hard. If you're up to putting together an old computer as a file server, you're not far from getting modern components, onboard SATA RAID, native GbE (and onboard video) (esp. stay away from crowding the PCI bus). Together with an affordable modern CPU and a decently-configured OS, this should be able to run rings around cheap consumer NAS boxes. But it requires some thinking and smart shopping, etc. OS pricing is an issue.

Obviously Linux for free has a cost advantage, and in the hands of the consumer NAS vendors, a pre-setup advantage. There are a couple of outs here -- get a pre-built suitable PC with XP thrown in cheaply (MCE is nicer for remote desktop); buy/re-use such an XP license; learn to set up and maintain Linux yourself.

I understand your "no GbE here" position, but it doesn't take much, and if you're buying/building a box, and interested in performance, and perhaps looking ahead, IMO it's in self-interest to not overlook the very attractive pricing of consumer GbE at present. Even if plugging into a 10/100 network, I'd look for a good onboard GbE solution to look ahead to the future.

The pre-built consumer NAS boxes can have some advantages: Cuteness, size, potential reduction in power consumption, OS already set up. Keyboard and monitor-free configuration.

SATA also has advantages looking ahead -- PATA support is being reduced; SATA is pretty much a must-have for RAID, and the cabling is cleaner. But if you're just looking at a drive or two, and SATA is a hinderance with some old computer, etc., I'd consider the alternatives (e.g. add-on SATA controller) and go with PATA if appropriate. PATA has an advantage of greater compatiblity with older devices, and will likely be supported for quite some time, at least as a single OS drive.

 

[RickGG]

100Base-T will only do around 10 MB/s at best
USB2 somewhere around 40 MB/s at best

So really, USB 2.0 bandwidth is a non-issue due to inferior 100B-T bandwidth.

If I were to build a NAS, I would definetely go with a RAID Array (at least level 1), and you are right, an older board would probably limit me to PATA, although I have seen some cheap SATA RAID boards out there from companies like ECS.

Gigabit LAN might be something I look into in the future, its just that for now, most of my workstations are 802.11G and my servers are on a nice Linksys WAP/Switch that only supports 100 Base-T.

As for the Linux option- this has always been interesting to me. Is SAMBA still the way to go for presenting linux volumes to the Windows world?

 

[Paperdoc]

I've seen recently some reports of actual data throughput testing on HDD's mounted in external enclosures, and the impact of the interface. Whether the HDD was SATA or PATA in the enclosure made little difference. Measured average data transfer rates were about the same for USB2 or Firewire 400 (IEEE 1394a) connections, slight advantage to Firewire. The new eSATA system produced better average speeds, ranging from twice as fast for an empty drive to just as fast as USB2 on a full drive. The fastest was an enclosure that used Firewire 800 (IEEE 1394b). NONE of them (nor, even, an internally-mounted SATA II drive) came even close to the MAX speeds specified for either SATA (original) or SATA II, so don't plan on achieving that MAX specification in any real world.

 

[RickGG]

Thanks, I figured as much. Just wanted to make sure I wasn't losing any real bandwidth by going with external USB 2.0 drive enclosures. So far, it has been my "poor man's silver bullet".