I'm playing with my new LTO9 tape drive (Tandberg/IBM one, SAS).
Some year ago, trying to find optimal parameters for an LTO-5 tape drive,
i've found:
options st buffer_kbs=16384
Minimum block size = 0
Maximum blocksize = 256K
Maximum Network Buffer Size = 262144
Maximum File Size = 25G
this lead to the LTO-9 unit:
*speed file_size=16 nb_file=4
btape: btape.c:1062-0 Test with zero data, should give the maximum throughput.
btape: btape.c:911-0 Begin writing 4 files of 17.17 GB with raw blocks of
262144 bytes.
[...]
btape: btape.c:385-0 Total Volume bytes=68.71 GB. Total Write rate = 592.4 MB/s
btape: btape.c:1074-0 Test with random data, should give the minimum
throughput.
btape: btape.c:911-0 Begin writing 4 files of 17.17 GB with raw blocks of
262144 bytes.
[...]
btape: btape.c:385-0 Total Volume bytes=68.71 GB. Total Write rate = 279.3 MB/s
btape: btape.c:1088-0 Test with zero data and bacula block structure.
btape: btape.c:966-0 Begin writing 4 files of 17.17 GB with blocks of 262144
bytes.
[...]
btape: btape.c:385-0 Total Volume bytes=68.71 GB. Total Write rate = 234.5 MB/s
btape: btape.c:1100-0 Test with random data, should give the minimum
throughput.
btape: btape.c:966-0 Begin writing 4 files of 17.17 GB with blocks of 262144
bytes.
[...]
btape: btape.c:385-0 Total Volume bytes=68.71 GB. Total Write rate = 223.8 MB/s
Trying to double all the value, as a starting point:
options st buffer_kbs=32768
Minimum block size = 0
Maximum blocksize = 512K
Maximum Network Buffer Size = 524288
Maximum File Size = 50G
lead to:
*speed file_size=16 nb_file=4
btape: btape.c:1062-0 Test with zero data, should give the maximum throughput.
btape: btape.c:911-0 Begin writing 4 files of 17.17 GB with raw blocks of
524288 bytes.
[...]
btape: btape.c:385-0 Total Volume bytes=68.71 GB. Total Write rate = 660.7 MB/s
btape: btape.c:1074-0 Test with random data, should give the minimum
throughput.
btape: btape.c:911-0 Begin writing 4 files of 17.17 GB with raw blocks of
524288 bytes.
[...]
btape: btape.c:385-0 Total Volume bytes=68.71 GB. Total Write rate = 279.3 MB/s
btape: btape.c:1088-0 Test with zero data and bacula block structure.
btape: btape.c:966-0 Begin writing 4 files of 17.17 GB with blocks of 524288
bytes.
[...]
btape: btape.c:385-0 Total Volume bytes=68.71 GB. Total Write rate = 247.1 MB/s
btape: btape.c:1100-0 Test with random data, should give the minimum
throughput.
btape: btape.c:966-0 Begin writing 4 files of 17.17 GB with blocks of 524288
bytes.
[...]
btape: btape.c:385-0 Total Volume bytes=68.71 GB. Total Write rate = 237.7 MB/s
So, a little better but not doubled the throughput, and this clearly was
expected.
So probably the optimal buffer size sit between 256K and 512K; but because
server have plenty of RAM, i think my search will stop here. ;-)
A queston rise on me: why 'bacula block structure' have a such great impact
on hardware compression?! EG, why if i write zeroes in raw mode i get 660.7 MB/s
while if i write zeroes in 'bacula block structure' i got 247.1 MB/s?!
Compressione seems correctly enabled:
root@svpve3:/etc/bacula# tapeinfo -f /dev/nst1
Product Type: Tape Drive
Vendor ID: 'IBM '
Product ID: 'ULTRIUM-HH9 '
Revision: 'Q3F5'
Attached Changer API: No
MinBlock: 1
MaxBlock: 8388608
SCSI ID: 2
SCSI LUN: 0
Ready: yes
BufferedMode: yes
Medium Type: 0x98
Density Code: 0x60
BlockSize: 0
DataCompEnabled: yes
DataCompCapable: yes
DataDeCompEnabled: yes
CompType: 0xff
DeCompType: 0xff
BOP: yes
Block Position: 0
Partition 0 Remaining Kbytes: -1
Partition 0 Size in Kbytes: -1
ActivePartition: 0
EarlyWarningSize: 0
NumPartitions: 0
MaxPartitions: 3
Thanks.
--
Ho ancora la forza di non tirarmi indietro, [...]
di far la conta degli amici andati e dire ``ci vediam più tardi''
(F. Guccini)
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