Let's see if anyone disagrees with me: Max throughput on a compressed LTO5 is 280 Mb/sec A single SATA would be too slow for this at 60-66 Mb sec; a RAID configuration with at least 5 or 6 disks would be necessary to get closer to 280 Mb/sec. (On a system such as a DELL MD1000, the first 10 disks contribute to throughput; the remaining 5 do not.)
However, a SAS drive can deliver 300 Mb/sec (theoretical); in practice 270 Mb/sec is more likely. I have neither the drive nor the server with the disks, so I am guessing. I imagine a RAID5 SAS disk configuration with at least 3 disks would be suitable for a holding disk with 2 LTO5 drives. Either that or a fully-loaded MD1000 with SATA drives. On Sun, Jul 18, 2010 at 6:07 PM, Dustin J. Mitchell <[email protected]> wrote: > On Thu, Jul 15, 2010 at 4:19 PM, Florian Lengyel > <[email protected]> wrote: >> We're attempting to get the specifications for the holding disk of an AMANDA >> server with 6GB SAS controllers that will be connected to an LTO5 drive. >> >> We want to know whether 7200 RPM SATA drives would be sufficiently fast >> for the holding disk (this will be a separate RAID unit), or do we need >> faster >> SAS drives to prevent shoe-shining? > > You should probably look at the raw *observed* throughput of your SATA > drives and of your tape drive, and then apply a healthy margin of > error. That margin accounts for any interference (e.g., interrupt > queueing) between the two subsystems, as well as filesystem overhead > on the SATA drives. This, of course, assumes that you have enough CPU > to move that much data. No, it's not particularly predictable - such > is life with a portable backup application! If Amanda was a hardware > appliance, the numbers would be much more predictable. > > Others may have some experience that they can share to help you out - > although with no replies in 3 days, maybe not.. > > Dustin > > -- > Open Source Storage Engineer > http://www.zmanda.com >
