msl 2024 1760 and 1840

[Ori Besser]

Hello,
I am going to purchase this library but I couldn't find any detailed documentation about the differences between ultrium 1760 and 1840. Beside the 1840 being faster , are there any more advantages? Is it a noticable speed improvement?
In addition, I've noticed that the 1840 version does not have a SAS version, only SCSI. so from an overall perception, which one will perform faster, the SAS 1760 or the SCSI 1840?

Thanks

[Uwe Zessin]

The 1760 is half-height and the 1840 is full-height.

In many (today the most?) environments the tape drive is not the limiting factor. For example, this week I've told a customer to move the servers with the most data first in the list (to keep concurrency as long as possible) and to defragment the disks.

A pretty raw calculation gave a throughput of about 27.7 MegaBytes/sec for a full backup using two old LTO-2 drives before this simple 'optimization'.

This morning I got feedback that the (incremental) backup ran faster (I didn't get any numbers, though).

[Ori Besser]

What exactly is the purpose of these half height/full-height configurations? Is there any advantage for choosing half-height. Does full-height always mean faster?


I got your point with the tape not being the bottleneck. It's an interesting thing to check though, I am going to connect mine to the most heavy-loaded server and the other severs will be backed-up through the network, I wander to what speed I would get. Theoretically I believe I should reach the tape speed.

[thomasr]

HP's half-hight drives are always a bit slower than the full-height drives, but in a given generation (LTO-4, for instance) all drives are the same native capacity. The Enterprise libraries require Fibre Channel drives, which are only available in full-height, so the half-height question is answered.

MSL libraries accept full-height or half-height drives. You might have a Fibre Channel SAN and want to use FC drives, so you'd get the full-height native Fibre Channel drives.

Or you might prefer SAS over parallel SCSI in the MSL, so you'd go with the half-height SAS drives.

In some cases, you'd have a choice -- for instance, pSCSI are offered both half- and full-height in the MSL. Standalone SAS drives are offered in both half- and full-height. Then how do you pick?

I'd pick first on the density requirement: do you need to deploy the devices in a server bay? Or in a 1U Rackmount enclosure? Or are you deploying a 3U Rackmount enclosure that needs to hold four drives? If so, you probably want the half-height drives.

On the other hand, if performance is your driver, get the somewhat faster full-height drives -- BUT BE CAREFUL to benchmark your servers, so you know that the servers can feed the full-height drives at the rate they'll need. It doesn't do you any good to buy an Ultrium 1840 drive (120MB/sec native) instead of an Ultrium 1760 drive (80MB/sec native) if your disks are only capable of feeding the tape drive at 50MB/second... and most people are surprised how often the disk, not the tape, is the bottleneck.

Worth noting: All HP LTO-4 tape drives support hardware encryption, regardless of form factor or interface. In the MSL libraries, the MSL Encryption Kit provides a great way to ensure that all your backup data is encrypted and secure from unauthorized eyes... but available to the business when you need to perform a restore.

Fun fact: If you ever get a chance to look at the bottom of the actual LTO half-height drive, you'll see cutouts where the motor winding show through.