On 08/18/2009 12:09 PM, James Bottomley wrote:
On Tue, 2009-08-18 at 11:53 -0400, Ric Wheeler wrote:
On 08/18/2009 10:57 AM, Greg KH wrote:
On Tue, Aug 18, 2009 at 09:59:56AM -0400, Ric Wheeler wrote:
On 08/18/2009 09:25 AM, Greg KH wrote:
On Tue, Aug 18, 2009 at 09:18:30AM -0400, Ric Wheeler wrote:
We have a new toy to test very large& slow storage with built up from 5
SAS expansion shelves (Promise Vtrak J-Class) with 60 S-ATA drives and
16 SAS drives (the S-ATA drives each have a Promise Vtrak S-ATA MUX
adapter daughter card in the disk sled).
The basic idea is to build a cheap& slow test bed for file& storage
system scalability. Collectively, we have about 120TB (raw) of capacity
to play with in one server.
As we work through various issues, a couple of oddities popped out.
The first is that udev grumbles during boot about "file name too long"
like the following:
Aug 17 06:49:58 megadeth udevd-event[20447]: unable to create db file
'/dev/.udev/db/\x2fdevices\x2fpci0000:00\x2f0000:00:04.0\x2f0000:17:00.0\x2f0000:18:0a.0\x2f0000:1f:00.0\x2fhost11\x2fport-11:0\x2fexpander-11:0\x2fport-11:0:0\x2fexpander-11:1\x2fport-11:1:0\x2fexpander-11:2\x2fport-11:2:17\x2fexpander-11:3\x2fport-11:3:1\x2fend_device-11:3:1\x2fbsg\x2fend_device-11:3:1':
File name too long
Odd, what is the sysfs tree for this device? You have expanders
attached to ports attached to expanders? How deep can you go?
thanks,
greg k-h
There are two dual-port SAS HBA's in the server that plug into the first of the
5 SAS expansion shelves. Each shelf has two internal SAS loops and is daisy
chained to the next shelf.... This test is running with just the first 4
shelves active (although that fifth shelf is plugged in, just not used/active).
Each of the 60 S-ATA disks sits behind a MUX card which lets it appear on both
loops.
We could break up the shelves into two independent sets of devices which would
limit the tree depth.
How can I get you the sysfs tree information in a useful way?
'tree /sys/devices/'
or
'find /sys/devices/'
would be good.
thanks,
greg k-h
Attached is the bzipped output from - the uncompressed output is quite
large. Note that this same server has CCIS controllers and fibre HBA's
as well,
It's perfectly legal the way you have it, but I will say you have an
inefficient configuration. The way a configuration like this is
supposed to look is that there should be a fanout expander at the top
going to the expander in each tray, for a routing depth of two for every
device.
The way you've got it: expander daisy chained off the next expander
gives an unnecessary routing delay to the disks furthest away in the
chain.
James
I understand that this configuration is not optimal, but from what I saw with
some commercial arrays, this is not an uncommon config (up to 4 shelves) when
going for capacity over performance.
Do you have a particular SAS fanout expander in mind? I suppose that we could
always add more hba's as well which would have other benefits...
Thanks!
Ric
--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
