[Bioclusters] Re: file server for cluster

Joe Landman bioclusters@bioinformatics.org
23 Apr 2002 13:27:00 -0400


  Mb/s = Mega bit per second. 
  MB/s = Mega byte per second (note the capitalized "b")

  1 bit = 0.125 byte, so 1 Mb/s -> 0.125 MB/s

  I would guess that most of what you quoted are MB/s, not Mb/s.

http://www.dell.com/us/en/esg/topics/segtopic_storage_scsi_main.htm you
see the 160 MB/s throughput.  This corresponds to 1280 Mb/s.

  The conversion is not completely accurate as there are protocol and
error detection/correction overheads.  I typically use a back of the
envelope of a factor of 10 conversion.  

  You can configure the unit on 
http://configure.us.dell.com/dellstore/config.asp?customer_id=555&order_code=PV220/221SCSI&s=biz to get a sense of the pricing.

On Tue, 2002-04-23 at 12:18, Ivo Grosse wrote:
> I just read that the throughput of the MaxAttach 6000 (with an IDE 
> RAID) is about 180 Mb/s, and that the throughput of Dell's PowerVault 
> 755N (with a SCSI RAID) is about 230 Mb/s.
> http://www.eweek.com/article/0%2c3658%2cs%253D702%2526a%253D21465%2c00.a
> sp
> Also, I heard that Dell's new PowerVault 755N based on Tualatins can 
> reach 470 Mb/s.

It is going to be bandwidth limited by the number of PCI busses, the
arrangement of IO, etc.  The specs say 3 PCI slots, but if they are on a
single PCI bus, you will be able to swamp the PCI with either 1 Ultra160
(for PCI-33), or 1 Ultra160+1 GigE card, or 2 Ultra160s.

Moreover, it has only 5 drive bays.  With the 73 GB drives, this is not
going to get you where you want to be.  You could use the Seagate 180 GB
drives (I have two myself).  5 of them get you to 0.9 TB.  No RAID, no
mirroring, simple JBOD.


> Naively, I had thought so far that striping over a dozen of disks gives 
> throughputs greater than 1 Gb/s.  Could you please comment on whether

... for sustained large block sequential reads with no other traffic on
the disks... 

> - the above examples are poor performers, and typical NAS servers give 
> a throughput greater than 1 Gb/s?,
> - it would make any sense to connect more than one Gigabit line from 
> the cluster switch to the file server?,
> - which NAS servers you would recommend that give a throughput of 1 
> Gb/s?, and
> - how much those beasts would cost?
> Thanks!
> Ivo
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Joseph Landman, Ph.D.
Senior Scientist,
MSC Software High Performance Computing
email		: joe.landman@mscsoftware.com
Main office	: +1 248 208 3312
Fax		: +1 714 784 3774