Date: Wed, 13 Apr 2016 15:58:24 +0100 From: Matthew Seaman <matthew@FreeBSD.org> To: freebsd-fs@freebsd.org Subject: zpool scrub makes zfs get slow? Message-ID: <570E5E90.7060107@FreeBSD.org>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --aFWt5r8pjleFi05DAAWV9ACtjvoXd0Qk5 Content-Type: multipart/mixed; boundary="U1D5aCBBcj7jIL4X5eaDX6fnniKlD9LLt" From: Matthew Seaman <matthew@FreeBSD.org> To: freebsd-fs@freebsd.org Message-ID: <570E5E90.7060107@FreeBSD.org> Subject: zpool scrub makes zfs get slow? --U1D5aCBBcj7jIL4X5eaDX6fnniKlD9LLt Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Part of our monitoring relies on running commands like: /sbin/zfs get -rHp -o value usedbysnapshots zroot through snmpd. We noticed today that this was timing out and it corresponded to a regular 'zpool scrub' starting up. While scrubbing is going on, that command can take in excess of a minute to return: % time /sbin/zfs get -rHp -o value usedbysnapshots zroot > /dev/null 0.298u 0.826s 1:08.62 1.6% 104+166k 47618+0io 0pf+0w % freebsd-version -ku 10.2-RELEASE-p9 10.2-RELEASE-p12 There's a large but not huge number of ZFSes in that pool: about 2500, and the drives are geli encrypted. Is this expected behaviour? Is there anything we can do to make 'zfs get' more snappy in these circumstances? Cheers, Matthew --U1D5aCBBcj7jIL4X5eaDX6fnniKlD9LLt-- --aFWt5r8pjleFi05DAAWV9ACtjvoXd0Qk5 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQJ8BAEBCgBmBQJXDl6WXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXQxOUYxNTRFQ0JGMTEyRTUwNTQ0RTNGMzAw MDUxM0YxMEUwQTlFNEU3AAoJEABRPxDgqeTnFhAQAIb13VzBnRc7uPVhVHFGrab9 EIu61OI4HWR/nt2kFpUOQ/MkOtFwXX2EW5tdC7BRpcTYf87o4jbeJ7oVCue4Ih5s 2Pzwv5r6M1sBkjXu8AiLdazLOXaxwtVoHD9meSNkVJ1unWv3E+wprrFVgB9DM1MO KGVKfetsNNRI6xifhuXZUcOIPrAqJZo6vz36QVNh3Bur7KOgum1dXt//sQ5HEri1 dzWFYdeXP2j9h6Plh5EnvzvcM7/vXEi0yRTjbY6wLixnV/G+OXMTl2LhuIq2vKWN UYoY9rPingy7lZxM7KOT5PYD7ULIVJ+6gnKymXsqUQo3g1WIAu/UD9fX8tf8kdFM BgiPM24RjN/DfpyzdVJM5cvXVoSzSTWSMMeo3fFLC/BjfZfeVaCKYyjPCPOIeUE8 Lfgl/+y/7gNePl49ayBFBQNDfrxqRTEIxzQFGJnriBRi2rgtyASsSycDlKb/kk/f zyzSTTLlgoR9O24AIe3YpiHOLtxrIdljHEX2uQmLRmvH7V0hF2Sy/+1/qZeam/vT GbNWX+Z9jZzhhc779G9yzOdxNZkv3O2WwhqWLEF6y1XKlKsVms+jVwCFS2CfuQFN v8GbMwhPp62I9I+Nr+rhle6dzj5DKY0FKXYSIgUsOAnwFphUqjuKo1Pjm4QO2JZV nwN47SCDGjojDPUQMkL9 =cZW/ -----END PGP SIGNATURE----- --aFWt5r8pjleFi05DAAWV9ACtjvoXd0Qk5--
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