-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 On 11/17/2013 06:54 PM, Douglas Gilbert wrote: > Even if the SCSI EH code does spin-up the disk, it is inefficient > and undesirable to send a device into EH for what is a normal, > predictable situation (i.e. that a SCSI disk will need a START STOP > UNIT (start) command as part of a resume operation). The device doesn't need the START STOP UNIT command as part of the resume operation; it only needs it prior to other commands. What is inefficient is starting up drives that won't be accessed. I don't see anything particularly inefficient about issuing the command in the eh path ( in fact, libata always uses the eh path to handle power management ). You can of course, use the manage_start_stop flag to have the disk start on resume if you really want. > A big server machine could have thousands of SCSI disks (many > potentially virtual). Sending them all into EH during a resume > would be a really good test for EH, but horrible for performance. > If I was designing the SCSI EH I would probably assume not all > disks would go into EH at roughly the same time. Also if that many > devices went into EH on the same controller (HBA) it might be > reasonable to assume that the controller they share needs > resetting. They don't all go into EH during resume; they go into EH when they are finally accessed, which for many of them is probably not for some time. This also sounds like a bit of speculation and/or hand waving. Is there really a problem with multiple devices going into EH? -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCgAGBQJSiWgGAAoJEJrBOlT6nu75klwIAK29G/p+pZhccbfXBnIpvq8m oIuCOCgMjIbSkJDEo52BiEf6d52tK8aQNTXcHZCC7T2/yvWV55vGHeXbxZ9iospp IsoJOMLtcM9p5DHZido5RubXrq63cU3yGovGbsp834Ij+d51HB17Dh4Dc1iU/mQV 4X6623hH0ooHWjmtoK6l5rGfKxkPe2ZKP3RAOpW5hiFaGPFWpc375Kukf6Zvw161 mBRfdWtc1SRGme/dcEEggH5t20R0kJteAey4RLF77W8VcooVbE3zCESpVNwqHxYK 6Mc67avVzMyk+Cmb2IN9iMB05oPDIzhKU4kStyYKVGqiS1D2NHUUi56GZTN5Ry0= =kmdB -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
