[Users] Is this "dd" operation harmful?
Hi, I found some "dd" operations were launched contiguously in my vdsm.log. Is this harmful? How was this operation caused?
From vdsm.log:
Dummy-51000::DEBUG::2012-10-11 15:38:57,243::__init__::1249::Storage.Misc.excCmd::(_log) 'dd if=/rhev/data-center/6f6d4801-7447-48ea-b516-627d83e7801e/mastersd/dom_md/inbox iflag=direct,fullblock count=1 bs=1024000' (cwd None) Dummy-51000::DEBUG::2012-10-11 15:38:57,305::__init__::1249::Storage.Misc.excCmd::(_log) SUCCESS: <err> = '1+0 records in\n1+0 records out\n1024000 bytes (1.0 MB) copied, 0.0388821 s, 26.3 MB/s\n'; <rc> = 0 Dummy-51000::DEBUG::2012-10-11 15:38:59,313::__init__::1249::Storage.Misc.excCmd::(_log) 'dd if=/rhev/data-center/6f6d4801-7447-48ea-b516-627d83e7801e/mastersd/dom_md/inbox iflag=direct,fullblock count=1 bs=1024000' (cwd None) Dummy-51000::DEBUG::2012-10-11 15:38:59,375::__init__::1249::Storage.Misc.excCmd::(_log) SUCCESS: <err> = '1+0 records in\n1+0 records out\n1024000 bytes (1.0 MB) copied, 0.0398412 s, 25.7 MB/s\n'; <rc> = 0 Dummy-51000::DEBUG::2012-10-11 15:39:01,383::__init__::1249::Storage.Misc.excCmd::(_log) 'dd if=/rhev/data-center/6f6d4801-7447-48ea-b516-627d83e7801e/mastersd/dom_md/inbox iflag=direct,fullblock count=1 bs=1024000' (cwd None) Dummy-51000::DEBUG::2012-10-11 15:39:01,445::__init__::1249::Storage.Misc.excCmd::(_log) SUCCESS: <err> = '1+0 records in\n1+0 records out\n1024000 bytes (1.0 MB) copied, 0.0393934 s, 26.0 MB/s\n'; <rc> = 0 Dummy-51000::DEBUG::2012-10-11 15:39:03,453::__init__::1249::Storage.Misc.excCmd::(_log) 'dd if=/rhev/data-center/6f6d4801-7447-48ea-b516-627d83e7801e/mastersd/dom_md/inbox iflag=direct,fullblock count=1 bs=1024000' (cwd None) Dummy-51000::DEBUG::2012-10-11 15:39:03,515::__init__::1249::Storage.Misc.excCmd::(_log) SUCCESS: <err> = '1+0 records in\n1+0 records out\n1024000 bytes (1.0 MB) copied, 0.0391104 s, 26.2 MB/s\n'; <rc> = 0 -- --- 舒明 Shu Ming Open Virtualization Engineerning; CSTL, IBM Corp. Tel: 86-10-82451626 Tieline: 9051626 E-mail: shuming@cn.ibm.com or shuming@linux.vnet.ibm.com Address: 3/F Ring Building, ZhongGuanCun Software Park, Haidian District, Beijing 100193, PRC
On Thu, Oct 11, 2012 at 03:44:25PM +0800, Shu Ming wrote:
Hi,
I found some "dd" operations were launched contiguously in my vdsm.log. Is this harmful? How was this operation caused?
That's storage.storage_mailbox.SPM_MailMonitor, polling for lvextend requests. dd is used, since in the old days, vdsm did not have storage.fileUtils.DirectFile. The behavior is expected, but I cannot say that it is harmless. The mailbox should be high on http://wiki.ovirt.org/wiki/Vdsm_TODO#refactoring since forking so much is a waste, as well as using strings instead of bytearrays. Making the module as a separate, testable entity, is important, too.
From vdsm.log:
Dummy-51000::DEBUG::2012-10-11 15:38:57,243::__init__::1249::Storage.Misc.excCmd::(_log) 'dd if=/rhev/data-center/6f6d4801-7447-48ea-b516-627d83e7801e/mastersd/dom_md/inbox iflag=direct,fullblock count=1 bs=1024000' (cwd None)
After reading the code, every mailbox should be 4096 byte size. And the total mailbox size is host * 4096. Ony one host is here, so the total mailbox size here is 4096. why should the 'dd' operation read 1024000 byte which is 1000K byte much lager than 4096 here? 2012-10-11 18:54, Dan Kenigsberg:
On Thu, Oct 11, 2012 at 03:44:25PM +0800, Shu Ming wrote:
Hi,
I found some "dd" operations were launched contiguously in my vdsm.log. Is this harmful? How was this operation caused? That's storage.storage_mailbox.SPM_MailMonitor, polling for lvextend requests. dd is used, since in the old days, vdsm did not have storage.fileUtils.DirectFile.
The behavior is expected, but I cannot say that it is harmless. The mailbox should be high on http://wiki.ovirt.org/wiki/Vdsm_TODO#refactoring since forking so much is a waste, as well as using strings instead of bytearrays. Making the module as a separate, testable entity, is important, too.
From vdsm.log:
Dummy-51000::DEBUG::2012-10-11 15:38:57,243::__init__::1249::Storage.Misc.excCmd::(_log) 'dd if=/rhev/data-center/6f6d4801-7447-48ea-b516-627d83e7801e/mastersd/dom_md/inbox iflag=direct,fullblock count=1 bs=1024000' (cwd None)
-- --- 舒明 Shu Ming Open Virtualization Engineerning; CSTL, IBM Corp. Tel: 86-10-82451626 Tieline: 9051626 E-mail: shuming@cn.ibm.com or shuming@linux.vnet.ibm.com Address: 3/F Ring Building, ZhongGuanCun Software Park, Haidian District, Beijing 100193, PRC
On Thu, Oct 11, 2012 at 11:38:19PM +0800, Shu Ming wrote:
After reading the code, every mailbox should be 4096 byte size. And the total mailbox size is host * 4096. Ony one host is here, so the total mailbox size here is 4096. why should the 'dd' operation read 1024000 byte which is 1000K byte much lager than 4096 here?
The controlling parameter is MAX_HOST_ID=250, not the number of current cluster members.
On 10/11/2012 09:44 AM, Shu Ming wrote:
Hi,
I found some "dd" operations were launched contiguously in my vdsm.log. Is this harmful? How was this operation caused?
dd is the way vdsm reads and writes data in its metadata luns of a storage domain. Each storage domain (except for nfs-based storage domains) has several special luns for managing the storage domain operations, one of them is the inbox which is used for communication between hosts about storage domains write operations that should executed by the SPM host etc. The only thing I'm not happy with is the usage of 'dd' instead of '/bin/dd'.
From vdsm.log:
Dummy-51000::DEBUG::2012-10-11 15:38:57,243::__init__::1249::Storage.Misc.excCmd::(_log) 'dd if=/rhev/data-center/6f6d4801-7447-48ea-b516-627d83e7801e/mastersd/dom_md/inbox iflag=direct,fullblock count=1 bs=1024000' (cwd None) Dummy-51000::DEBUG::2012-10-11 15:38:57,305::__init__::1249::Storage.Misc.excCmd::(_log) SUCCESS: <err> = '1+0 records in\n1+0 records out\n1024000 bytes (1.0 MB) copied, 0.0388821 s, 26.3 MB/s\n'; <rc> = 0 Dummy-51000::DEBUG::2012-10-11 15:38:59,313::__init__::1249::Storage.Misc.excCmd::(_log) 'dd if=/rhev/data-center/6f6d4801-7447-48ea-b516-627d83e7801e/mastersd/dom_md/inbox iflag=direct,fullblock count=1 bs=1024000' (cwd None) Dummy-51000::DEBUG::2012-10-11 15:38:59,375::__init__::1249::Storage.Misc.excCmd::(_log) SUCCESS: <err> = '1+0 records in\n1+0 records out\n1024000 bytes (1.0 MB) copied, 0.0398412 s, 25.7 MB/s\n'; <rc> = 0 Dummy-51000::DEBUG::2012-10-11 15:39:01,383::__init__::1249::Storage.Misc.excCmd::(_log) 'dd if=/rhev/data-center/6f6d4801-7447-48ea-b516-627d83e7801e/mastersd/dom_md/inbox iflag=direct,fullblock count=1 bs=1024000' (cwd None) Dummy-51000::DEBUG::2012-10-11 15:39:01,445::__init__::1249::Storage.Misc.excCmd::(_log) SUCCESS: <err> = '1+0 records in\n1+0 records out\n1024000 bytes (1.0 MB) copied, 0.0393934 s, 26.0 MB/s\n'; <rc> = 0 Dummy-51000::DEBUG::2012-10-11 15:39:03,453::__init__::1249::Storage.Misc.excCmd::(_log) 'dd if=/rhev/data-center/6f6d4801-7447-48ea-b516-627d83e7801e/mastersd/dom_md/inbox iflag=direct,fullblock count=1 bs=1024000' (cwd None) Dummy-51000::DEBUG::2012-10-11 15:39:03,515::__init__::1249::Storage.Misc.excCmd::(_log) SUCCESS: <err> = '1+0 records in\n1+0 records out\n1024000 bytes (1.0 MB) copied, 0.0391104 s, 26.2 MB/s\n'; <rc> = 0
-- Thanks, Rami Vaknin, QE @ Red Hat, TLV, IL.
participants (3)
-
Dan Kenigsberg -
Rami Vaknin -
Shu Ming