LTO-8 very slow 115Mbyte/s ... please help

[WillyEB70]

Dear all,

I still have a performance issue with a newly purchased Ultrium LTO-8. When I write files to tape, I can't go faster than 115-120MB/s. This unit, however, has a declared speed of about 300MB/s.

Now I will describe the environment in which I conducted the tests.

I have an HPE Pro

liant 560G8 server with 128GB of RAM, two HBAs,  SAN network (8Gbps) with two HP Brocade 8/20, an HP StoreEver 8G2 with the LTO-8 drive with two 8Gbps FC HBAs. The firmware is N4Q1/MSL Series FC.

The server Proliant uses Alamalinux 9.4 and I have not installed additional HPE drivers.

The test I performed was this:

 tar -cvf /dev/st0 /backup/foo.dd

tar: Removing leading `/' from member names

/backup/foo.dd

real    14m45.137s

user    0m21.883s

sys     3m9.250s

aboout 115Mbyte/s

the foo.dd file was stored in an HPE MSA P2000 storage which has performance of about 800MB/s.

How can I improve this throughput ?

How I can see if this drive use hardware compression  ? 

Thanks in adavance for your help.

Best Regards

"Willy"

[Curtis_Ballard · Accepted solution]

Have you tried different block sizes?  As I recall tar typically defaults to 512 bytes for historical 512 byte drives and using "-b 512" to send 512 of those 512 byte blocks for a transfer size of 256K is recommended for tape.

[WillyEB70]

Dear Curtis,

with your magic number "512" my LTO-8 is running faster:

time tar -b 512 -cvf /dev/st0 /backup/foo.dd
tar: Removing leading `/' from member names
/backup/foo.dd

real 4m27.277s
user 0m1.660s
sys 0m48.723s

this time means about 370MBytes/s but my file is produced if dd if=/dev/zero

I'm going to test again with different files , thanks for now.

Best Regards

-Willy-

[WillyEB70]

Dear Curtis dear all

to my great surprise only the first tar went very well, all the others that I am running with the same file and with the same block are going very slowly around 100Mbyte/s:

[root@infn-vm05 enrico]# time tar -b 512 -cvf /dev/st0 /backup/foo-100GB.dd
tar: Removing leading `/' from member names
/backup/foo-100GB.dd

real 16m3.813s
user 0m1.776s
sys 1m17.683s

Any ideas ?

Best Regards

-Willy-

[WillyEB70]

Dear ll,

Using "-b 512" I get a better speed but the  I don't understand why is that I also have to use /dev/nst0 (no rewind), if I use /dev/st0 (rewind) I get very modest writing and reading speed, has I showed above.
kind regards

-Willy-

[Curtis_Ballard]

I haven't tried timing tar for many years.  I wonder if perhaps the timing method you are using is including the rewind time which will be highly variable.  LTO is serpantine so it writes along the whole tape then turns around and writes back to the beginning.  If a write ends close to the physical beginning of the tape then the rewind is very fast, if a write ends near the physical end of the tape the rewind will take much longer.  It seems like the no rewind device file would give you the most accurate timing since it completely removes any question of measuring time spent on a rewind.

[NarayanKK-SO]

@WillyEB70

Did you try backing up the local data (not from MSA) and test it with the said block size and rewind option ?

Also use LTT to check the device health by running device performance and system performance.

Hope this helps.