On Sat, 2012-03-24 at 11:45 -0400, Doug Hughes wrote:
> On 3/24/2012 6:42 AM, Conrad Wood wrote:
> >
> > Mostly I wonder if it is atall possible to get such speeds over QDR. Are
> > you in a position where you could perhaps run a "cp" followed by "sync"
> > on an infiniband attached storage system?
> >
> >
> indeed it is. Many of the larger integrated vendors are moving to QDR
> based SANs for that reason. speeds in excess of 6GBytes/sec and up on
> sequential loads are not uncommon. (with the appropriate back-end storage)
The sequential speed of Infiniband QDR is fantastic, but our clients (I
guess rightly) complain about the speed of 'cp'. The same 'cp' on the
local array runs lightning fast.
That's what I don't understand: Why is the same sequence of commands so
extraordinarily different on local vs remote storage?
I don't think I have mentioned the sequence of commands in details, it
is:
MOUNTPOINT=/tmp/[randomstuff]
mbytes=4G
1. mkdir ${MOUNTPOINT}
2. mkfs -t ext4 -F ${MOUNTPOINT}
3. dd if=/dev/zero of=${MOUNTPOINT}/randomfile.bin bs=1M \
count=$mbytes oflag=direct
4. sync
5. STARTTIME=time()
6. cp ${MOUNTPOINT}/randomfile.bin ${MOUNTPOINT}/randomfile2.bin
7. sync
8. umount ${MOUNTPOINT}
9. ENDTIME=time()
and now the speed is calculated by simply ($ENDTIME-$STARTTIME)/$mbytes
This sequence is run 5x in parallel on different volumes and the sum of
all tests is the total throughput.
The total sum is >1000 MByte/s on the storage server locally, but only
~150MByte/s over SRP.
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