{"id":294,"date":"2010-02-02T15:31:16","date_gmt":"2010-02-02T20:31:16","guid":{"rendered":"http:\/\/jamesdevine.info\/?p=294"},"modified":"2010-02-02T15:31:16","modified_gmt":"2010-02-02T20:31:16","slug":"xen-cannot-run-more-than-4-vms","status":"publish","type":"post","link":"https:\/\/jamesdevine.info\/index.php\/2010\/02\/xen-cannot-run-more-than-4-vms\/","title":{"rendered":"Xen Cannot Run More Than 4 VMs"},"content":{"rendered":"

I have been setting up a test Xen 3.3 box running on Ubuntu 8.04. I have been getting the following error: “Device xxxx <\/em>(vbd) cannot be connected. failed to find an unused loop device”\u00a0\u00a0where xxxx is some number. It turns out that by default only 8 loopback devices are enabled. The following command shows how many loopback devices are enabled:<\/p>\n

ls -l \/dev\/loop*<\/pre>\n
To increase the number of loopback devices the following line needs to be added to the \/etc\/modules file. I used a value of 64 so I can run up to 32 virtual machines.<\/p>\n
add loop max_loop=64<\/pre>\n
Now when you run\u00a0ls -l \/dev\/loop* you will see additional loopback devices.<\/span><\/pre>\n
 <\/span><\/p>\n
root@xen-server:~# ls -l \/dev\/loop*<\/div>\n
brw-rw—- 1 root disk 7, \u00a00 2009-07-09 03:43 \/dev\/loop0<\/div>\n
brw-rw—- 1 root disk 7, \u00a01 2010-02-02 15:22 \/dev\/loop1<\/div>\n
brw-rw—- 1 root disk 7, 10 2010-02-02 15:22 \/dev\/loop10<\/div>\n
brw-rw—- 1 root disk 7, 11 2010-02-02 15:22 \/dev\/loop11<\/div>\n
brw-rw—- 1 root disk 7, 12 2010-02-02 15:22 \/dev\/loop12<\/div>\n
brw-rw—- 1 root disk 7, 13 2010-02-02 15:22 \/dev\/loop13<\/div>\n
brw-rw—- 1 root disk 7, 14 2010-02-02 15:22 \/dev\/loop14<\/div>\n
brw-rw—- 1 root disk 7, 15 2010-02-02 15:22 \/dev\/loop15<\/div>\n
brw-rw—- 1 root disk 7, 16 2010-02-02 15:22 \/dev\/loop16<\/div>\n
brw-rw—- 1 root disk 7, 17 2010-02-02 15:22 \/dev\/loop17<\/div>\n
brw-rw—- 1 root disk 7, 18 2010-02-02 15:22 \/dev\/loop18<\/div>\n
brw-rw—- 1 root disk 7, 19 2010-02-02 15:22 \/dev\/loop19<\/div>\n
brw-rw—- 1 root disk 7, \u00a02 2010-02-02 15:22 \/dev\/loop2<\/div>\n
brw-rw—- 1 root disk 7, 20 2010-02-02 15:22 \/dev\/loop20<\/div>\n
…<\/div>\n","protected":false},"excerpt":{"rendered":"
I have been setting up a test Xen 3.3 box running on Ubuntu 8.04. I have been getting the following […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[17,23,26,37],"tags":[],"class_list":["post-294","post","type-post","status-publish","format-standard","hentry","category-linux","category-topics-in-virtualization","category-server","category-xen"],"aioseo_notices":[],"jetpack_featured_media_url":"","jetpack-related-posts":[{"id":300,"url":"https:\/\/jamesdevine.info\/index.php\/2010\/03\/sedf-cpu-scheduler-in-xen\/","url_meta":{"origin":294,"position":0},"title":"sEDF CPU Scheduler in Xen","author":"James Devine","date":"March 2, 2010","format":false,"excerpt":"By default the Xen Hypervisor uses the credit CPU scheduler. The sEDF (simple earliest deadline first) CPU\u00a0scheduler\u00a0can be used by setting the sched boot parameter equal to sedf. The easiest way to do this is by editing the grub boot loader config file, menu.lst. The file is located in \/boot\/grub\/menu.lst.\u2026","rel":"","context":"In "General"","block_context":{"text":"General","link":"https:\/\/jamesdevine.info\/index.php\/category\/general-information\/"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":377,"url":"https:\/\/jamesdevine.info\/index.php\/2011\/12\/move-netapp-root-volume-vol0-to-a-new-aggrigate\/","url_meta":{"origin":294,"position":1},"title":"Move NetApp Root Volume (vol0) to a New Aggrigate","author":"James Devine","date":"December 2, 2011","format":false,"excerpt":"By default vol0 is the root volume on a NetApp storage device and is stored on aggregate aggr0. After accidentally assigning too many disks to aggr0 I found the need to decrease the size of the aggregate. 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Infrastructure can and does fail for a myriad of reasons, e.g., natural failure rates of hardware, natural disasters, power, network, cooling. 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