Maximum write speed of HP Ultrium 1760 drive

The write speed of the HP Ultrium 1760 drive is specified as 120MB/s with LTO-4 media and 80MB/s with LTO-3 media. However I get half of that - 80/40 MB/s respectively. The connector is SFF-8482 at the drive and SATA at the controller. The SFF-8482 technically supports 2 SAS lanes and there are cables SFF-8482 to 2x SATA (second photo). However I'm not sure if:

1. The drive supports 2 SAS lanes
2. If it'll work just pluggin a SFF-8482 to 2x SATA cabke in two of the ports of my controller
3. If it'll make any difference since the drive and controller are 3 GBit/s which theoretically is 300 MB/s and should be enough bandwidth to reach 120 MB/s actual read/write speed.
4. The SFF-8482 to 2x SATA are a bit rare - I found the one from the third photo on aliexpress. However i'm not sure if it'll fit phisically on the SAS controller. Probably not - the spacing ont he controller looks bigger.

I did try plugging it to windows and running some diagnostic tools from HP and it mentioned something like "the drive is not running to full speed."

• Controller LSI Logic SAS 3041E
• Cable used: the blue one from the first photo
• Tape drive: HP Ultrium 1760 drive
• CPU: an old Intel Core 2 Quad Q9400 @ 2.66GHz
• RAM: 8GB
• OS: CentOS 7
• Storage 4 disks in ZFS raidz (RAID-5), read speed: 230-350MB/s, write speed ~150MB/s (edited)
• cpu usage

Update: HDD speed is not the problem:

dd if=/dev/zero of=$TAPE bs=1M count=5000 5000+0 records in 5000+0 records out 5242880000 bytes (5.2 GB) copied, 67.8001 s, 77.3 MB/s

SAS runs at least 3 Gbit/s = 300 MB/s goodput. The drive is rated at 120 MB/s max (240 MB/s w/ 2:1 compression), so adding the second lane doesn't do anything.

Your SAS HBA uses SATA-style ports but they're totally fine for 3 Gbit/s.

Basically, your problem lies elsewhere.

• Are you writing an image or from file level? The latter can be much slower with small files than the theoretical sequential speed of your RAID group. Run a recursive copy against /dev/null and you'll see.
• The 3041E is a RAID controller, which might not handle a tape drive properly. Try a simple HBA or the 3041E in HBA mode, if supported.