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>> GlancePlus is old and it won't report correctly disk performance on a SAN.
no thats not the case - you just have to know what the stats are telling you...
in glance "disk utilization" (and %busy in sar -d) simply tells you what percentage of time during a measurement interval a particular disk or LUN was actually servicing some sort of IO - now it doesn't take into account what that disk is actually capable of doing in terms of IO, simply how much time it is busy doing something. Now obviously you could see 2 disks on a system, one of which is an old 10K RPM 36GB physical disk, and another which is a LUN presented from a disk array which actually might be made up of dozens of 15K RPM disks fronted by a load of cache. To sar or glance, these devices look the same - they are both devices of type sdisk - but if they both show close to 100% utilization/%busy what does that mean? Well it might mean a lot to the physical disk, but probably isn't very important for the SAN LUN. Of course there are other stats in both glance and sar which are much more relevant, but the sar values Michael has pointed you at are a good starting point.
HTH
Duncan
I am an HPE Employee
no thats not the case - you just have to know what the stats are telling you...
in glance "disk utilization" (and %busy in sar -d) simply tells you what percentage of time during a measurement interval a particular disk or LUN was actually servicing some sort of IO - now it doesn't take into account what that disk is actually capable of doing in terms of IO, simply how much time it is busy doing something. Now obviously you could see 2 disks on a system, one of which is an old 10K RPM 36GB physical disk, and another which is a LUN presented from a disk array which actually might be made up of dozens of 15K RPM disks fronted by a load of cache. To sar or glance, these devices look the same - they are both devices of type sdisk - but if they both show close to 100% utilization/%busy what does that mean? Well it might mean a lot to the physical disk, but probably isn't very important for the SAN LUN. Of course there are other stats in both glance and sar which are much more relevant, but the sar values Michael has pointed you at are a good starting point.
HTH
Duncan
I am an HPE Employee
Fidel,
Don't see any points assigned...
I don't use gpm, but I do use glance, and for disks generally look at the IO by Disk screen (press 'u' in glance or just launch glance with "glance -u")
In there the _real_ interesting metric is the last column (Serv Time) - this is the same as "avserv" from sar -d. You want to see this below 10ms for a well performing system, and anything over 20ms is usually a cause for concern.
In addition the Phys IO column is pretty interesting as this tells us how many IOs per second the LUN is handling - a physical disk spindle is typically capable of handling over 100 IOs per second, and most stuggle with over 200 IOs pers second, but that's really in _very_ broad hand waving terms as it can depend on many factors associated with data location/disk geometry and IO sizes etc.
More than that is difficult to say from a "generalities" perspective. As with all performance measuring, the thing to do is have a picture of what the system looks like when performance is good, and then compare that to when you have a performance issue.
HTH
Duncan
I am an HPE Employee
Don't see any points assigned...
I don't use gpm, but I do use glance, and for disks generally look at the IO by Disk screen (press 'u' in glance or just launch glance with "glance -u")
In there the _real_ interesting metric is the last column (Serv Time) - this is the same as "avserv" from sar -d. You want to see this below 10ms for a well performing system, and anything over 20ms is usually a cause for concern.
In addition the Phys IO column is pretty interesting as this tells us how many IOs per second the LUN is handling - a physical disk spindle is typically capable of handling over 100 IOs per second, and most stuggle with over 200 IOs pers second, but that's really in _very_ broad hand waving terms as it can depend on many factors associated with data location/disk geometry and IO sizes etc.
More than that is difficult to say from a "generalities" perspective. As with all performance measuring, the thing to do is have a picture of what the system looks like when performance is good, and then compare that to when you have a performance issue.
HTH
Duncan
I am an HPE Employee
