On 24/10/14 07:59, Jon LaBadie wrote:
> On Thu, Oct 23, 2014 at 04:28:01PM +1100, Tom Robinson wrote:
>> Now I have to work out why my tape is reporting as smaller! amtapetype
>> reports my tape is only half
>> as big for the same block size...(was 1483868160 is now 743424512). :-/
>>
>> Checking for FSF_AFTER_FILEMARK requirement
>> Applying heuristic check for compression.
>> Wrote random (uncompressible) data at 67415370.8307692 bytes/sec
>> Wrote fixed (compressible) data at 273874944 bytes/sec
>> Compression: enabled
>> Writing one file to fill the volume.
>> Wrote 761266700288 bytes at 57975 kb/sec
>> Got LEOM indication, so drive and kernel together support LEOM
>> Writing smaller files (7612661760 bytes) to determine filemark.
>> device-property "FSF_AFTER_FILEMARK" "false"
>> define tapetype ULT3580-TD5 {
>> comment "Created by amtapetype; compression enabled"
>> length 743424512 kbytes
>> filemark 987 kbytes
>> speed 57975 kps
>> blocksize 512 kbytes
>> }
>> # for this drive and kernel, LEOM is supported; add
>> # device-property "LEOM" "TRUE"
>> # for this device.
>>
>>
> Note it is not only reporting the lower size, but dumps
> are experiencing it as well.
>
> IIRC, you are using an LTO-5. My peek at the web says
> that format can record at up to 280Mbps. You are now
> only seeing 58Mbps. Is that a big change from your
> previous runs?
>
> Feeding a drive too slowly, i.e. below its ability to
> stream continuously, can reduce the apparent capacity
> of the tape.
>
> If this is the case you may have to find ways to
> increase the data flow rate to your drive.
>
> JonThanks Jon. I was getting 'speed 73464 kps', previously. So, yes, there is some performance degradation. I never saw anything close to 280Mbps in my tests with amtapetype. Is there another way to accurately test tape write performance? Regards, Tom
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