extreme performance degradation - ext3/sata
Hi,
I've encountered a problem with sata drives and ext3/reiser, which I documented in the correspondence with Neil Brown below. He referred me to your forum. Since I'm not subscribed please cc my return address.
Regards
Dragan
Quoted 34 lines
Quoted 34 lines
I have extreme performance degradation when writing to ext3fs on SATA drives, about 7 times slower than reading from the same volume - 17 MB/s writing, 120 MB/s reading.
The problem also affects reiserfs in the same way, however xfs appears to be immune to this problem. It reads AND writes to the same volume at about 100 MB/s, which is the same speed at which null-bytes from
/dev/zerocan be poured into the raw volume.My setup is: SuSE 8.2 (2.4.20), Siemens Scenic W600 (i865g), P4/3GHz, 2GB PC2100 RAM, a SCSI boot/swap/root disk, 6 Maxtor 250 GB SATA drives, 2 on on-board connectors, 4 on 2 Promise SATA 150 Tx2+ PCI 32/33 controllers (pdc-ultra.o).
The volumes have been formatted with commands like:
mke2fs -J device=/dev/sda2
/dev/md0
mkreiserfs -j/dev/sda2/dev/md0
mkfs.xfs -l logdev=/dev/sda2/dev/md0whereby "
/dev/md0" may also be "/dev/vg01/lvol1".The performance degradation, as well as the steady performance of xfs, is totaly independent of the disk clustering mode, e.g. 5-way RAID5, 6-way RAID5, 3-way RAID0 of 2-way RAID1, 2-way RAID0 (for higher priority on-board controller), 4-way RAID0 (for slightly slower PCI controllers), using either software raid or LVM.
I wish I could give you more info to help you pin-point the performance killer. Please let me know, what more I can do to help.