Hello I own a Venus T5C mini box based on a JMicron JM393 controller, used in pure port multiplier mode (no JBOD, no RAID). It is plugged in eSATA to a QNAP TS-119 NAS which runs a 2.6.37 kernel on a Marvell Kirkwood 88F6281. When I first started copying data on any disk of the external box, I realized the write speed was low (read speed is OK). Testing with dd and various block sizes shows that the larger the block size, the higher the throughput is. On my NAS, I determined the work buffer size of the cp command to be approximately 8KB. With a 8KB blocksize, when writing a 16MB file with dd on one of the disks, I average at 6,5 MB/s write speed. It is already a great improvement compared to the 393 KB/s write speed I obtained on a 2.6.36 kernel, but it is low compared to results I obtain with higher blocksizes (52,4 MB/s with 4MB blocksize) or using other hardware (laptop with Intel ICH9M-E/M controller reaches 286 MB/s with 8KB blocksize using a 2.6.31 kernel). When I take one of the disks out and connect it in eSATA with a basic external case, I reach 37,6 MB/s with 8KB blocksize. This result is pretty constant whatever the blocksize value I tested (from 1KB to 16MB, doubling each time). Please let me know what information is needed to have a better understanding of this issue. Thanks in advance for your help. -- Sylvain -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
