On 08.11.2010 09:13, DJ wrote: > > After scratching my head for a few weeks, I've decided to ask for some help. > > First, I've got two machines connected by gigabit ethernet, network > performance is not a problem as I am able to substantially saturate the wire > when not using iscsi [say iperf] or ftp. Both systems are 8.1-RELENG. They > are both multi-core, 8G of RAM. > > Symptoms: When doing writes (size relatively independent) from a client to a > server via iSCSI I seem to be > hitting a wall between 18-26MB/s of write. This can be repeated continuously > whether doing a newfs on a 2TB iscsi volume or doing a dd from /dev/zero to > the iscsi target. I haven't compared read performance. What originally put me > on to this was watching the newfs *fly* across the screen, and then hang for > several seconds, and then *fly* again, and > then pause.
I'll snip down this mail a little bit to ask some control questions (having recently had quite a wrestle with iSCSI myself). -Is jumbo frames involved? (and enabled on the initiator, all switches in between, and the target) -What's the number of PPS (some switches have PPS issues, which becomes painfully relevant for small block IO)? (I got rid of most of my problems when I replaced the Netgear GS724Tv3 switch with a Cisco SG-300) -Are you running digests? -Do you have TSO/TSOv2 enabled at the endpoints? -Does top -HSC reveal anything? -Does systat -vmstat 1 reveal anything? -What's the ICMP (ping) roundtrip times between the initiator and target IPs? //Svein -- --------+-------------------+------------------------------- /"\ |Svein Skogen | sv...@d80.iso100.no \ / |Solberg Østli 9 | PGP Key: 0xE5E76831 X |2020 Skedsmokorset | sv...@jernhuset.no / \ |Norway | PGP Key: 0xCE96CE13 | | sv...@stillbilde.net ascii | | PGP Key: 0x58CD33B6 ribbon |System Admin | svein-listm...@stillbilde.net Campaign|stillbilde.net | PGP Key: 0x22D494A4 +-------------------+------------------------------- |msn messenger: | Mobile Phone: +47 907 03 575 |sv...@jernhuset.no | RIPE handle: SS16503-RIPE --------+-------------------+------------------------------- A: Because it fouls the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail? ------------------------------------------------------------ Picture Gallery: https://gallery.stillbilde.net/v/svein/ ------------------------------------------------------------
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