filer gurus --
got a question about tape drive performance, when directly attached to the filer (via SCSI).
We have an F825 (soon to upgraded, we hope !) to which we've attached both an LTO-2 and LTO-3 8-tape library unit (these are from Dell, just FYI). The LTO-3 is a recent acquisition, and so we thought we'd run a few tests, to confirm that the LTO-3 drive is "faster". Well, it isn't - at least doesn't appear to be, based on an overnight full backup of the filer.
Now, I know there are a lot of things to watch out for when making tests like this, but I though I'd check with the group here to see if anyone knows...
- is there a way to tell what the data rate to the tape drive is from the filer, over the SCSI bus ? I'm looking for more of an instantaneous measurement, rather than the overall average of (amount of data moved / time it took).
- anyone else played around with this (ie, attempting to measure the data throughput from filer to SCSI attached tape drive) ? If so, what did you try, and what conclusions did you reach ?
Thanks much for your replies and time !
John
sysstat 1
in the last few columns you will see tape I/O (read and write columns) in KB/sec
Remember, if you have "wide" directories with lots of small files, your tape I/O will only be as fast as the filer can get them off disk.
I have an R200, depending on the data I get 13-17MB/sec for about 30-40 million files. (literally hundreds of thousands of entries per directory with many directories) over 3-5TB all the way to 60-80 MB/sec for directories with large files (usually thousands to low millions of files over 2-3 TB)
This is to local attached LTO-3 (via FCAL).
I used to have AIT-3 that topped out at 15MB/sec with compression. (really slow for the multi-TB dumps)
--tmac
On 10/18/07, John Foley johnf@comm.mot.com wrote:
filer gurus --
got a question about tape drive performance, when directly attached to the filer (via SCSI).
We have an F825 (soon to upgraded, we hope !) to which we've attached both an LTO-2 and LTO-3 8-tape library unit (these are from Dell, just FYI). The LTO-3 is a recent acquisition, and so we thought we'd run a few tests, to confirm that the LTO-3 drive is "faster". Well, it isn't - at least doesn't appear to be, based on an overnight full backup of the filer.
Now, I know there are a lot of things to watch out for when making tests like this, but I though I'd check with the group here to see if anyone knows...
is there a way to tell what the data rate to the tape drive is from the filer, over the SCSI bus ? I'm looking for more of an instantaneous measurement, rather than the overall average of (amount of data moved / time it took).
anyone else played around with this (ie, attempting to measure the data throughput from filer to SCSI attached tape drive) ? If so, what did you try, and what conclusions did you reach ?
Thanks much for your replies and time ! John--
John Foley < johnf@comm.mot.com > sent from Windows using Thunderbird
On Thu, Oct 18, 2007 at 11:06:00AM -0500, John Foley wrote:
- is there a way to tell what the data rate to the tape drive is from the filer, over the SCSI bus ? I'm looking for more of an instantaneous measurement, rather than the overall average of (amount of data moved / time it took).
Are you looking at sysstat? It has a tape performance column.
- anyone else played around with this (ie, attempting to measure the data throughput from filer to SCSI attached tape drive) ? If so, what did you try, and what conclusions did you reach ?
What is the rate you're getting?
Is this with 'dump' or some commercial backup package? I might want to compare the speed between the backup package, just running a 'dump' on the same filesystem (will eliminate the production of catalog history data), and running a dump to the 'null' device. If the filer is under load, the tape drive may not be your bottleneck.
-
A Darren Dunham -
John Foley -
tmac