Date: Wed, 02 Mar 2005 17:37:06 +0300 From: Deomid Ryabkov <myself@rojer.pp.ru> To: freebsd-geom@freebsd.org Subject: gvinum mirror seems to use only one disk for reading Message-ID: <4225CF92.80800@rojer.pp.ru>
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This is a cryptographically signed message in MIME format. --------------ms070107080307020606080108 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit I have a gvinum-based mirrored setup and i noticed that only one disk gets the load of read requests. for example: toxin[~rojer]# dd if=/dev/gvinum/usr of=/dev/null & vmstat 1 [1] 70487 procs memory page disks faults cpu r b w avm fre flt re pi po fr sr da0 da1 in sy cs us sy id 1 1 0 75580 158780 337 0 0 0 395 4 0 0 384 681 1015 4 3 93 1 0 0 75580 158780 3 0 0 0 3 0 0 1964 6376 4138 58340 0 49 51 0 1 0 75580 158780 0 0 0 0 0 0 0 1998 6455 4197 59243 0 52 48 0 1 0 75580 158780 0 0 0 0 0 0 2 1948 6307 4111 57759 1 50 50 0 1 0 75580 158780 0 0 0 0 0 0 0 2007 6492 4217 59502 2 48 50 0 1 0 75580 158780 0 0 0 0 0 0 1 1979 6400 4154 58707 0 48 51 the relevant disk tps values are: disks da0 da1 0 0 0 1964 0 1998 2 1948 0 2007 1 1979 notice that only da1 is busy reading, da0 is completely idle. there is also an oddity when writing to gvinum. writes go to both drives as they should and tps numbers are the same, as expected, but "time spent processing requests" is different for da0 and da1. (this number is displayed as "disk percent load" in systat -vmstat). e.g., when running dd if=/dev/zero of=/usr/test & systat -vmstat 2 i get output similar to the following: Disks da0 da1 KB/t 128 128 tps 83 83 MB/s 10.40 10.40 % busy 30 16 the difference stays at about the same value (30 vs 15-17). the question is... why is that? :) -- Deomid Ryabkov aka Rojer myself@rojer.pp.ru rojer@sysadmins.ru ICQ: 8025844 --------------ms070107080307020606080108 Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIJIzCC AuwwggJVoAMCAQICAwwKdjANBgkqhkiG9w0BAQQFADBiMQswCQYDVQQGEwJaQTElMCMGA1UE ChMcVGhhd3RlIENvbnN1bHRpbmcgKFB0eSkgTHRkLjEsMCoGA1UEAxMjVGhhd3RlIFBlcnNv bmFsIEZyZWVtYWlsIElzc3VpbmcgQ0EwHhcNMDQwMzMxMjIxODA5WhcNMDUwMzMxMjIxODA5 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