----- Original Message ----- From: "Al Boldi" <a1426z@xxxxxxxxx> To: "JaniD++" <djani22@xxxxxxxxxxxxx> Cc: <linux-raid@xxxxxxxxxxxxxxx> Sent: Sunday, November 27, 2005 6:40 PM Subject: Re: RAID0 performance question > JaniD++ wrote: > > Al Boldi wrote: > > > Neil Brown wrote: > > > > On Saturday November 26, djani22@xxxxxxxxxxxxx wrote: > > > > > The cat /dev/nb# >/dev/null makes ~ 350 Mbit/s on each nodes. > > > > > The cat /dev/nb0 + nb1 + nb2 + nb3 in one time parallel makes > > > > > ~780-800 Mbit/s. - i think this is my network bottleneck. > > > > > > How much do you get w/ nb0+1,2,3 and nb0+1+2,3 respectively? > > > > I unable to test write, because this is a productive system. > > Think this value is about 75-80 per node and ~200-250 in md31. > > How much do you get with: > cat nb# + nb# > /dev/null > cat nb# + nb# + nb# > /dev/null > respectively? md1 = 280- 291Mbit md1+md2 = 450-480 Mbit md1+md2+md3 = 615-630 Mbit md1+md2+md3+md4 = now the peak is 674 Mbit.... ...on a lightly used online system. (~44Mbit download + ~60Mbit upload) This time dd if=/dev/md1 of=/dev/null bs=1M count=4096 what i have used. I think, this is normal. I have try the md31 with different readahead settings: 1. nb0,1,2,3 + md1,2,3,4 readahead = 0 and md31 readahead =4096 result: 380 Mbit 2 all readahead . = 0 result: 88-98 Mbit 3. nb0,1,2,3 + md1,2,3,4 readahead = 2048 and md31 readahead = 0 result: 88-96 Mbit - I wonder! :-O 4. nb# + md# readahead = 0 and md31 readahead = 8192 result: 96-114 Mbit The winner is my default profile :-D all 2048 and md31 = 4096 result : 403-423 Mbit Neil! What do you say? :-) > > > > > > But the cat /dev/md31 >/dev/null (RAID0, the sum of 4 nodes) only > > > > > makes ~450-490 Mbit/s, and i dont know why.... > > > > > > > > > > Somebody have an idea? :-) > > > > > > > > Try increasing the read-ahead setting on /dev/md31 using 'blockdev'. > > > > network block devices are likely to have latency issues and would > > > > benefit from large read-ahead. > > > > > > Also try larger chunk-size ~4mb. > > > > Ahh. > > This is what i can't do. :-( > > I dont know how to backup 8TB! ;-) > > Maybe you could use your mirror!? There is no mirrors! This is only further options! To be able easy replace, repair one node.... Thanks Janos > > -- > Al - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
