On 04/01/99 00:34:34 you wrote:
That was my first reaction as well.
And this was my second. Try creating the file "fresh" (via copy) and then reading it (later, after you're sure it's no longer in cache) and seeing the results. Also, I suspect having fewer than 7 drives could be a limiting factor.
And this was my third. The in-cache response doesn't seem to be out of line given other possible variables.
Bruce
On Thu, 1 Apr 1999 sirbruce@ix.netcom.com wrote:
What sort of guidelines do people follow when deciding on the minra setting? At one end of the spectrum, you have broadcast video streaming servers that deal exclusively with long, sequential reads. At the other end, you have something like an INN server storing articles in individual files. Are there any tools to help decide which setting is best, or do you just "eyeball" it and try both settings and see which one seems better?
Also, I suspect having fewer than 7 drives could be a limiting factor.
A single drive should be able to sustain 8MB/sec or higher just on its own... a stripe of five drives should hit at least 40MB/sec. sysstat on that filer does in fact report 38 to 43MB/sec disk reads during a "vol scrub".
My simple rule is minra=on for crazy apps like INN what have tons of small totally random I/O's and minra=off for almost anything else. Basically, if you think caching will help you in any way you want minra off.
Actually, the 9GB SCSI drives I believe you're using are only rated for a max (not sustained) external transfer rate of 5MB/sec, so the numbers you're seeing really make sense to me. FYI, the max external transfer (not sustained) rate for our 18GB FC-AL drives is a much nicer 12.5MB/sec so you would probably see better (although not necessarily double <g>) sequential performance with those....
-Val. ============================================== Val Bercovici Office: (613)724-8674 Systems Engineer Pager: (800)566-1751 Network Appliance valb@netapp.com Ottawa, Canada FAST,SIMPLE,RELIABLE ==============================================
On Thu, 1 Apr 1999, Val Bercovici (NetApp) wrote:
Ah, okay, so the crossover point is much closer to the "millions of tiny files" end of the spectrum. We have a bunch of F230's with "split" mailbox spools (about 3.5 million inodes) which are still probably better off with minra=on, although another pair with traditional monolithic mailboxes ought to have minra turned off then.
Only 5MB/sec? That doesn't sound right to me, especially for a 7200-rpm FC-AL drive (the ST19171FC's). The narrow SCSI Quantum in my workstation gets 8.1MB/sec on sequential block reads averaged across the entire drive.
-
Brian Tao -
sirbruce＠ix.netcom.com -
Val Bercovici (NetApp)