With the response time discrepancy, I would think it's likely that the fast response time on writes is due to caching.
You say that this is the only volume on the SAN seeing these times. I assume that this is the only host accessing that LUN? Is that the only LUN being accessed by this host? --Matt On Tue, Sep 16, 2014 at 12:01 PM, Ski Kacoroski <[email protected]> wrote: > On 09/16/2014 08:39 AM, Alan Robertson wrote: > >> On 09/16/2014 09:12 AM, Ski Kacoroski wrote: >> >>> Hi, >>> >>> We installed a new student records system over over the summer that >>> runs on MS SQL server. Everything seems to be ok, but for one thing >>> that I am not sure is an issue waiting to bit me or something I can >>> ignore. On the SAN, the volume for the transaction logs has 125ms >>> read response times (write response times are around 2ms). This is >>> the only volume on the SAN with such large response times. Has anyone >>> seen this before and if so, is it something I need to be concerned about. >>> >> Since write times are fast, then it's not likely a SAN congestion >> issue. Is the transaction log RAID5? Are there rebuilds in progress? >> >> 125ms is really really slow. It's about 10x slower than the real >> underlying disk - including seek times. Unless you have a rebuild >> underway, it sounds broken to me. >> >> If you can afford it (and you probably can), I'd recommend RAID10 for >> transaction logs - or even RAID1 SSD (even though it's pricey, >> transaction logs aren't usually huge). >> > > The disks are RAID1+0, 10k. And yes I agree something is fishy here as > this the only place I see the problem on the SAN. > > We are no where near the maximum IOPs on the array so that is not the > problem. > > I am not sure about SAN disk alignment - I will check on this with the > vendor. > > Thanks for all the replies. > > cheers, > > ski > > -- > "When we try to pick out anything by itself, we find it > connected to the entire universe" John Muir > > Chris "Ski" Kacoroski, [email protected], 206-501-9803 > or ski98033 on most IM services > _______________________________________________ > Discuss mailing list > [email protected] > https://lists.lopsa.org/cgi-bin/mailman/listinfo/discuss > This list provided by the League of Professional System Administrators > http://lopsa.org/ >
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