From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Mamedov Subject: RAID5/6 slow due to a member device -- how to diagnose? Date: Thu, 3 Mar 2016 19:30:26 +0500 Message-ID: <20160303193026.7d08e64b@natsu> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_/KE/kxrd7f0HEM5fHdj.xQgf"; protocol="application/pgp-signature" Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/KE/kxrd7f0HEM5fHdj.xQgf Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable Hello, Let's suppose I am seeing slow write performance on a RAID5 or RAID6, and I= am suspecting that it's because of one of its devices operating slower than others (maybe a soft-failing or just low-performing hard drive, in case with non-identical member drives). Nothing in dmesg, no timeouts or ATA errors or anything like that. How would I go about diagnosing which device that is (if any) is slowing do= wn the array, aside from performance-testing each individual device (which see= ms rather difficult if it's only slow on writes, not reads). In 'top' there's of course high iowait, 50-70% all the time during writes. = But is that broken down somewhere to show which particular block device is being the most 'waited for'? --=20 With respect, Roman --Sig_/KE/kxrd7f0HEM5fHdj.xQgf Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iEYEARECAAYFAlbYSoUACgkQTLKSvz+PZwjzNgCfVHcbogGpnixFDU1S3bKuWrVg nHwAn36WyXNDJqpOL3d5CB3K40b3niE5 =+M1h -----END PGP SIGNATURE----- --Sig_/KE/kxrd7f0HEM5fHdj.xQgf--