[CentOS] Need advice on storage

Tue Nov 13 06:47:35 UTC 2007
boisvert.guy at videotron.ca <boisvert.guy at videotron.ca>

----- Message d'origine -----De: "redhat at mckerrs.net" <redhat at mckerrs.net>Date: Lundi, Novembre 12, 2007 10:28 pmObjet: Re: Re : Re: [CentOS] Need advice on storageÀ: CentOS mailing list <centos at centos.org>> > > Guy, > > how many drives can the server take ? and how many are there in > it just now ? > > I'd even go as far as to say install the OS and the data on the > 3 x 320gb sata drives and ditch the 80gb IDE. That is what I do > and it is one of the strengths of software raid, the fact that > you can mix and match raid types on the same physical disks. I'd > go for a triple mirror for /boot and install the rest of the OS > on the RAID-5 set or along with the data (grub can't boot of > raid-5 as far as I'm aware). > > > Alternatively if re-installing or copying your current OS onto > new drives is not practical at this point I'd get 2 x 320g > drives mirror them and also get that extra 1gb of RAM. The extra > RAM could make more of a difference than 10k rpm drives. I dont > think that you'll get anywhere near the performance you'd expect > from a stripe compared to a mirror. As mentioned earlier, > Raptors, IMO, are overrated and they are way hotter and noisier > due to their higher spindle speed. > > How is the box performing ? what are you noticing when it is > slow ? Wait IO ? Can you determine if it is IO bound or CPU > bound ? > > > Cheers, > > Brian. > The server can physically take 5 drives.As for RAM, suggestion taken.  I'll go buy 1 more Gig.  I know that Linux is aggressive when using RAM / Cache so i can just help.When all clients are connected and when they seem to refresh their mail cache and office activity is high, %iowait goes up to 45-55.  I have a script that check and log lsof used by Communigate (every 5 minutes).  Sometimes, i see lsof as high as 130 000.  I had to raise a couple of parameter (in sysctl.conf and limits.conf)because we had Communigate disconnecting clients and i saw messages like:IMAP the 'accept' call failed. Error Code=too many files open in this processI'll probably start another thread for this problem.  The default settings of CentOS for open files were very low.  I had to raise the values and now i'm at 300 000 and i Communigate still display errors from time to time even if my not so precise lsof logging script never shows more than 130 000.  I had even "too many files" errors  with lsof log showing as low as 65 000.  I'm a little confused.  Maybe i'll need more elaborate debugging tools. As you said, i'm in a case where migrating system drive to a RAID 5 array wouldn't be easy.But i have a new possible solution that arosed when i went to see the physical system tonight:  There is a Promise VTRAK 15100 SCSI enclosure in the rack with a free SCSI bus and space to put new SATA drives inside.  I think we have a spare Adaptec 39160 so tomorrow, i'll check that (it's a PCI-X card  but i think it should work PCI too).  If i have the Adaptec, then i'll probably buy 4 x Western-Digital 250 Gigs "YS" (RAID serie) @ about 75$ each, put them inside the VTRAK and configure them in RAID 10 for a total of 500 Gigs.  I briefly checked the VTRAK documentation and they were talking about "up to 200 MBps" throughput and support for NCQ.  It remains to be seems how it could perform with 4 disks in RAID 10.  But it should easily beat a single 200 Gigs IDE drive!For now, i did hdparm -t /dev/hdc (stoopid IDE mail drive!) and it gave me 38.21 MB/sec.Thanks!Guy Boisvert
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