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+++ This bug was initially created as a clone of Bug #664882 +++

Hi,

SPM hosts produce ~ 2000 iops, some times even more, every 2 seconds.

This is probably because the periodic inbox reads are being done as the following:

dd if=[path_to_inbox] iflag=direct bs=512 count=2000, while the total size of it  is only 1M

This situation heavily impacts customers SAN.

Thanks,

Vladik

Fixed.
Tested on RHEL6 with vdsm-4.9-47.el6.x86_64,

Before fix dd wrote 512 byte for 2000 times:

Dummy-4556::DEBUG::2011-02-08 11:08:00,896::storage_mailbox::626::Storage.Misc.excCmd::(_checkForMail) 'dd if=/rhev/data-center/ade9f73e-272a-42bb-8b8c-bb3288e0637e/mastersd/dom_md/inbox iflag=direct bs=512 count=2000' (cwd None)

While after fix dd wrote 1M for 1 time:

Dummy-3241::DEBUG::2011-02-08 16:35:45,982::storage_mailbox::632::Storage.Misc.excCmd::(_checkForMail) 'dd if=/rhev/data-center/ade9f73e-272a-42bb-8b8c-bb3288e0637e/mastersd/dom_md/inbox iflag=direct,fullblock count=1 bs=1024000' (cwd None)

Although it's hard to see the exact iops number using iostat, the tps column shows that the inbox's DM device have low iops average which get lower consistently..