Veli Cakmak put forth on 2/25/2010 3:48 AM: > The PC with SATA disk gives below rate (value) 7200 rpm > > 1000000+0 records in > > 1000000+0 records out > > 1024000000 bytes (1.0 GB) copied, 5.55338 s, 184 MB/s (this is proxy server > with 100 users)(sw raid1)
I dare say 184MB/s write throughput doesn't seem possible with software mirroring of two 7.2K rpm SATA disks. Mirrored writes are going to be slightly slower than single disk writes. The fastest sequential write 7.2K rpm SATA disks are the 2TB models from Seagate and they max out at around 130MB/s with an average write speed of around 105MB/s. If that 184MB/s figure for a pair of mirrored disks is accurate, I want to know what disks you have so I can order one! Something else to keep in mind is that the filesystem you're writing the output file to is going to affect write throughput. Filesystems reside atop partitions, and the placement/location on the disk of the partition you're writing to also will make a difference in sequential write speed. The closer the partition is to the outside of the disk platter(s) the faster the read/write throughput will be. Are you testing writes to the same filesystem type on all those machines or to different FS types? I happen to have both EXT2 and XFS filesystems on one of my server disks. Here are sequential write results from my Western Digital WD5000AAKS-00V1A0 single platter 500GB 7.2K rpm SATAII disk using kernel 2.6.31.1 (self rolled, all drivers in kernel), sata_sil, NCQ disabled, elevator=deadline: EXT2 /$ dd conv=fsync if=/dev/zero of=bigfile.txt bs=1024 count=1000000 1000000+0 records in 1000000+0 records out 1024000000 bytes (1.0 GB) copied, 16.6619 s, 61.5 MB/s XFS /$ dd conv=fsync if=/dev/zero of=bigfile.txt bs=1024 count=1000000 1000000+0 records in 1000000+0 records out 1024000000 bytes (1.0 GB) copied, 19.6523 s, 52.1 MB/s As you can see, XFS, being a journaled FS, has considerably slower sequential write throughput compared to EXT2, a non journaled FS. However, note the 1024 block size. Let's see what happens when we change the block size to 4096 to match the XFS block size. XFS 4096 block size /$ dd conv=fsync if=/dev/zero of=bigfile.txt bs=4096 count=100000 100000+0 records in 100000+0 records out 409600000 bytes (410 MB) copied, 5.8053 s, 70.6 MB/s Matching the XFS block size increased write throughput by almost 20MB/s. Not bad eh? ;) Remember to always compare apples to apples and not apples to oranges, or your results will be confusing and have little meaning. When you run each test, make sure you use a block size that is optimally matched to the underlying filesystem you're writing your test output files to. Hope this information helps you out in one way or another. Cheers. -- Stan -- To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org Archive: http://lists.debian.org/4b867501.1070...@hardwarefreak.com
