VLS LTO compression slows down throughput by 60%

[JonT_1]

I have been trying to improve DP5.5 backup speed to a VLS6840 with LTO-3 emulation.

Using LTT 4.1sr1 I can get 143MB/s to an LTO drive with compression disabled, but only 58MB/s with compression enabled.

(Block size is 64k, LTT compression is tested at 2:1, host is Windows 2k3.

A 60% degradation with VLS compression turned on is NOT what I expected - any ideas?

[Kevin Collins_11 · Accepted solution]

Hi,

The software compression implementation does in fact reduce the performance of the device, independent of which emulation is being used. That is a tradeoff of using software compression to achieve higher capacities in the device.

Regards,

Kevin

[JonT_1]

Thanks Kevin - I understand that compression doesn't come free, but I expected maybe 10% or so, after all compression is a standard technique. 60% reduction on a single write stream seems excessive - could this be a bug?