Hi I''ve a setup with opensource xen3.0.3 on debian etch. lately i''m experiencing problems with the main debian domu, which runs samba cyrus apache and few other services. i''m having very high machine load due to iowait at 100%. i suppose the culprit to be cyrus, but i''m not sure. i have 4.5g mail, split in something like 100000 files. I already remounted my partition with noatime,nodiratime as suggested by the cyrus site, but didn''t help. The vm has only 1 virtual disk of 100gb, 70% free, on lvm. is there anything xen could be involved in? thanks maxxer -- Lorenzo Milesi - lorenzo.milesi@yetopen.it YetOpen S.r.l. - http://www.yetopen.it/ C.so E. Filiberto, 74 23900 Lecco - ITALY - Tel 0341 220 205 - Fax 178 607 8199 GPG/PGP Key-Id: 0xE704E230 - http://keyserver.linux.it -------- D.Lgs. 196/2003 -------- Si avverte che tutte le informazioni contenute in questo messaggio sono riservate ed a uso esclusivo del destinatario. Nel caso in cui questo messaggio Le fosse pervenuto per errore, La invitiamo ad eliminarlo senza copiarlo, a non inoltrarlo a terzi e ad avvertirci non appena possibile. Grazie. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
How is this disk connected to the VM? XEN''s backend methods of connecting disks through dom0 aren''t great for high I/O use - one of the classic caveats to virtualization in general is that you don''t run your database server or your e-mail server in a VM. While this may not be true per se, it still indicates that things like e-mail servers have out-of-the-ordinary requirements for disk I/O. If you''re using the "file:" method for this disk in the domU, I suggest trying "tap:aio:" instead. Also, you may want to try using an iSCSI target/initiator setup (even if the initiator is done in software) to see if that helps. -Nick>>> On 2008/06/06 at 05:06, Lorenzo Milesi <lorenzo.milesi@yetopen.it> wrote:Hi I''ve a setup with opensource xen3.0.3 on debian etch. lately i''m experiencing problems with the main debian domu, which runs samba cyrus apache and few other services. i''m having very high machine load due to iowait at 100%. i suppose the culprit to be cyrus, but i''m not sure. i have 4.5g mail, split in something like 100000 files. I already remounted my partition with noatime,nodiratime as suggested by the cyrus site, but didn''t help. The vm has only 1 virtual disk of 100gb, 70% free, on lvm. is there anything xen could be involved in? thanks maxxer -- Lorenzo Milesi - lorenzo.milesi@yetopen.it YetOpen S.r.l. - http://www.yetopen.it/ C.so E. Filiberto, 74 23900 Lecco - ITALY - Tel 0341 220 205 - Fax 178 607 8199 GPG/PGP Key-Id: 0xE704E230 - http://keyserver.linux.it -------- D.Lgs. 196/2003 -------- Si avverte che tutte le informazioni contenute in questo messaggio sono riservate ed a uso esclusivo del destinatario. Nel caso in cui questo messaggio Le fosse pervenuto per errore, La invitiamo ad eliminarlo senza copiarlo, a non inoltrarlo a terzi e ad avvertirci non appena possibile. Grazie. This e-mail may contain confidential and privileged material for the sole use of the intended recipient. If this email is not intended for you, or you are not responsible for the delivery of this message to the intended recipient, please note that this message may contain SEAKR Engineering (SEAKR) Privileged/Proprietary Information. In such a case, you are strictly prohibited from downloading, photocopying, distributing or otherwise using this message, its contents or attachments in any way. If you have received this message in error, please notify us immediately by replying to this e-mail and delete the message from your mailbox. Information contained in this message that does not relate to the business of SEAKR is neither endorsed by nor attributable to SEAKR. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Lorenzo Milesi wrote:> Hi > > I''ve a setup with opensource xen3.0.3 on debian etch. > lately i''m experiencing problems with the main debian domu, which runs > samba cyrus apache and few other services. > i''m having very high machine load due to iowait at 100%. i suppose the > culprit to be cyrus, but i''m not sure. i have 4.5g mail, split in > something like 100000 files. I already remounted my partition with > noatime,nodiratime as suggested by the cyrus site, but didn''t help. The > vm has only 1 virtual disk of 100gb, 70% free, on lvm. > is there anything xen could be involved in?I would guess its imap thats causing your problem. What kind of disk back end is the vm on? I know you said lvm but is that lvm on a hardware raid, software raid, if so how many disks and what raid level? Ive had a web/mail server in the past that iowait was just tearing up performance. I migrated imap mail off to a different machine and that made a *huge* difference. That was just a single disked server with no hardware or software raid. I know people have said don''t run a database or email in a vm but it seems to me all that needs to be addressed is having a fast storage back end. I hope I am right, as I plan to migrate our database and mail servers to virtual machines. Initially they will be on the same piece of hardware but eventually they will on separate dom0s. I know in the meantime there will be some IO contention but I am hoping that I can mitigate some of that with relatively fast IO back end and a lot of RAM. -- Nick Anderson <nick@anders0n.net> http://www.cmdln.org http://www.anders0n.net _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Op vrijdag 6 juni 2008 15:11, schreef Nick Anderson:> Lorenzo Milesi wrote: > > Hi > > > > I''ve a setup with opensource xen3.0.3 on debian etch. > > lately i''m experiencing problems with the main debian domu, which runs > > samba cyrus apache and few other services. > > i''m having very high machine load due to iowait at 100%. i suppose the > > culprit to be cyrus, but i''m not sure. i have 4.5g mail, split in > > something like 100000 files. I already remounted my partition with > > noatime,nodiratime as suggested by the cyrus site, but didn''t help. The > > vm has only 1 virtual disk of 100gb, 70% free, on lvm. > > is there anything xen could be involved in? > > I would guess its imap thats causing your problem. What kind of disk > back end is the vm on? I know you said lvm but is that lvm on a hardware > raid, software raid, if so how many disks and what raid level? > > Ive had a web/mail server in the past that iowait was just tearing up > performance. I migrated imap mail off to a different machine and that > made a *huge* difference. That was just a single disked server with no > hardware or software raid. > > I know people have said don''t run a database or email in a vm but it > seems to me all that needs to be addressed is having a fast storage back > end. I hope I am right, as I plan to migrate our database and mail > servers to virtual machines. Initially they will be on the same piece of > hardware but eventually they will on separate dom0s. I know in the > meantime there will be some IO contention but I am hoping that I can > mitigate some of that with relatively fast IO back end and a lot of RAM.I must say that we have great problems with extremely high IOWAIT, possibly due to the raid card not being fully hardware raid (allthough we had requested it). We even used the tap:aio, but it made no difference. I hope the new card will solve our problems, but maybe xen has a problem too. our machines don''t even use that much disk in the first place... -- Maarten Vanraes BA NV: IT & Security _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Maarten Vanraes wrote:> I must say that we have great problems with extremely high IOWAIT, possibly > due to the raid card not being fully hardware raid (allthough we had > requested it). > > We even used the tap:aio, but it made no difference.tap:aio could be part of your problems as well. Its my understanding that under heavier workloads tap:aio which is still file based does not perform as well as a direct disk or lvm. And on the storage thing, Yes it is kind of a pain that you need many disks to get faster speeds, and it seems like all they make is large disks anymore. I suppose just look at the extra storage as good backup locations :) How many disk are in your raid set? What hardware raid card did you order? I would highly recommend a BBU on that raid card. I know for 3ware cards specifically there is up to 10% performance increase with BBU present. -- Nick Anderson <nick@anders0n.net> http://www.cmdln.org http://www.anders0n.net _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users