The main snag with with tape cartridges is that too locate information the tape must be read from the beginning. This is very time consuming and ineficient if only a small amount of data is to be recovered.
Where a drive supports a compression algorithum the corresponding performance, and capacity figures are included. This presupposes that the data to be backed up is readily compressible like text or HTML files.
If the data to be backed up is already compressed, {.jpg, .gif, .Z, .z, } the drives compression option will not provide any additional compression and may in some cases slow the backup down or reduce the capacity.
The following table is sorted by backup speed. Prices are idicative only, additional charges for cables, controlers, racks, etc may be applicable.
Model | Media | Performance | Capacity | Interface | Mounting | Guide | ||
---|---|---|---|---|---|---|---|---|
Native | Compresed | Native | Compresed | type | style | Price | ||
7207-011 | QIC(1/4-inch) | 200KB/s | N/A | 525MB | N/A | SCSI | Table Top | |
7207-012 | QIC(1/4-inch) | 300KB/s | N/A | 1.2GB | N/A | SCSI | Table Top | |
7207-122 | QIC(1/4-inch) | 380KB/s | 760KB/s | 4GB | 8GB | SCSI-2 | Table Top | £1,160 |
7206-005 | 4mm DDS-2 Data Cartridge | 400KB/s | 800KB/s | 4GB | 8GB | SCSI-2 | Table Top | £1,739 |
7208-011 | 8mm Data Cartridge | 500KB/s | 1MB/s | 5GB | 10GB | SCSI-2 | Table Top | |
7206-110 | 4mm DDS-3 Data Cartridge | 1.1MB/s | 2.2MB/s | 12GB | 24GB | SCSI-2 | Table Top | £1,904 |
7207-315 | QIC(1/4-inch) | 1.5MB/s | 3.0MB/s | 13GB | 26GB | SCSI-2 | Table Top | £3,240 |
3570-B00 | Magstar MP Fast Access Linear Tape | 2.2MB/s | 6.6MB/s | 5GB | 15GB | SCSI-2 Differential | External | £5,611 |
3490-E01 | 1/2-inch | 3MB/s | 6.8MB/s | 0.8GB | 2.4GB | SCSI-2 | Table Top | |
3490-F01 | 1/2-inch | 3MB/s | 6.8MB/s | 0.8GB | 2.4GB | SCSI-2 | Deskside | £15,778 |
3490-F11 | 1/2-inch | 3MB/s | 6.8MB/s | 0.8GB | 2.4GB | SCSI-2 | Rackmount in FC0 Rack | £15,778 |
7208-341 | 8mm Data Cartridge | 3MB/s | 6MB/s | 20GB | 40GB | SCSI-2 | Table Top | £3,900 |
7205-311 | 1/2-inch DLT | 5MB/s | 10MB/s | 35GB | 70GB | SCSI-2 differential | Table Top | £7,577 |
3570-C00 | Magstar MP Fast Access Linear Tape | 7.0MB/s | 15.0MB/s | 5GB | 15GB | SCSI-2 Differential | External | £9,828 |
3590-B11 | 1/2-inch | 9MB/s | 13MB/s | 10GB | 30GB | SCSI-2 | Rack mount | £22,943 |
3590-E11 | 1/2-inch | 14MB/s | 34MB/s | 20GB | 60GB | Ultra SCSI | Rack mount | £32,107 |
With regard to performance the figures given are for the tape drive with the data being supplied at an optimum block size. If the next block of data is not available to the drive when it is ready for it, the drive must stop and wait. Given that hard disks can have a sequential access rate of as little as 50KB/s.
It is vary easy to find especially with the faster tape drives that the
tape drive is waiting for the disks, rather than the system waiting for the
tape drive. With the faster drives the source files must be on a striped or
mirrored LV to make use of the tape drives speed.
If backup performance falls below half the expected speed, check
vmstat
or iostat
while a file backup is running.
If these show the system to be disk bound check for file fragmentation, other
wise it may be worth trying a larger block size if possible.
Tape Drive Dencity settings
Some dives support multiple density setings.
{the lsattr command lists attributes density_set_1, and density_set_2}
Density
Drive
Description
00
*
Hardware default for drive
2
1/2 inch 9-Track Tape
1600 bpi
3
1/2 inch 9-Track Tape
6250 bpi
15
QIC
DC600A/DC6000 60MB QIC-120 cartridge
16
QIC
DC6150/MC6150 150MB QIC-150 cartridge
17
QIC
DC6525/MC6525 525MB QIC-525 cartridge
19
4mm DDS3 drive
2GB DDSiii cartridge {2:1 compression posible}
20
8mm 5GB
2.3GB mode
21
QIC
QIC1000 1GB cartridge
21
8mm 5GB
5GB mode no hardware compression
23
35GB 7205-311
DLTtapeIII cartridge 2.6GB no hardware compression
24
35GB 7205-311
DLTtapeIII cartridge 6GB no hardware compression
25
35GB 7205-311
DLTtapeIII cartridge 10GB {2:1 compression posible}
25
35GB 7205-311
DLTtapeIIIxt cartridge 15GB {2:1 compression posible}
26
35GB 7205-311
DLTtapeIV cartridge 20GB {2:1 compression posible}
27
35GB 7205-311
DLTtapeIV cartridge 35GB {2:1 compression posible}
33
QIC
QIC-5010-DC 13GB cartridge
34
QIC
QIC-2GB 2GB cartridge
36
4mm DDS3 drive
4GB DDS2 cartridge {2:1 compression posible}
37
4mm DDS3 drive
12GB DDS3 cartridge {2:1 compression posible}
39
8mm 20GB
20GB mode hardware compression if configured
140
8mm 5GB
5GB mode hardware compression if configured
15
QIC
15
QIC
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