[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-users] RESOLVED: bad I/O performance with HP Smart Array RAID
Timh B wrote: Yes, we are almost exclusively running SAS disk, so comparing to SATA disks may not be fair. It's well probable that different experiences rely on the controller not supporting SATA well. We usually use SATA disks in preference just in order to have another option for a possible disaster recovery scenario. Normal SATA vs SAS performance is normally not an issue for us, the 100-150MB/s you get normally out of a RAID 10 4-drive SATA array has always been sufficient - but of course not the HP e200i 10-15MB/s. Even though sub-30mb writes is really low, perhaps the cciss driver is not good enough or compatible with xen-kernels? As far as I see (look at the thread I pointed you to) the people complaining about horribly poor performance are running a wide range of different kernel versions, most of them non-Xen. So, I assume it is nota Xen issue. Also, I've seen quite a few complaints of Windows users, so the issue does not seem to be a Linux driver issue, either. It's most probably an issue between the controller and the drives - that might be a reason why people are complaining that enabling BBWC does not help at all (well, a few megs of cache is filled in milliseconds), while enabling the drives' write cache seems to have solved the issue for many users. What were the exact measurements you used? Oh, just the silly old "dd" to a large file and to an LVM volume - the danger with "dd" is to get higher throughput figures because of caching effects, so it is ok for determining max figures. But of course I did test after getting complaints about the performance and after seeing myself a DRBD mirror syncing with only about 10MB/s, either (after having suspected someone had plugged the server into a FastEthernetport I was quite surprised to see that this was not a network issue at all). Best regards, Tom -- ------------------------------------------------------------------------ Thomas Aeby, Kirchweg 52, 1735 Giffers, Switzerland Voice : (+41)26 4180040 Internet: aeby@xxxxxxxxxx PGP public key available ------------------------------------------------------------------------ _______________________________________________ Xen-users mailing list Xen-users@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-users
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |