On Thu, 21 Aug 2003 [EMAIL PROTECTED] wrote: >Hi > >> > > * IDE drives die around 10 concurrent users. Fast SCSI or FC drives are >> > > manditory for a large number of concurrent users. The faster the better. >> > >> > Can anyone else comment on the disk requirements ? >> > >> > Does more RAM help ? >> > >> > What, exactly, is so great about SCSI ? >> > >> > The platters turn at the same speed - is it the elevator algorithm seek >> > and the out-of-order replies ? >> > >> > I /really/ don't want to have to go the SCSI route. >> > >> > I tried Software RAID5, but the rebuild after a power cut was painful. >> Andy, going backwards: >> trust us, the "grownups" - you very, very much *want* to go the >> SCSI route. There are reasons for higher prices - the disk electronics are >> way more advanced, the request queueing really works, the wide data path >> allows for *sustained* high throughput, the otpitmized head movement >> traslates into faster reads and writes and into longer hardware life. And, >> no, serial ata is *not* as good as scsi. >> software raid - try harder, or go hardware raid with hot swappable >> drives (scsi, of course :-) >> more ram helps big time - ram is good, more ram is even gooder. > ><smiles> >> trust us, the "grownups" - you very, very much *want* to go the > >Please give info. please: >I tested a compaq proliant with UW SCSI, 10 lts workstations >against a ATA100 IDE. >hdparm -t -T /dev/hda <sda> gives a slight edge to the IDE. >For most part the two machines felt the same. > >I missed the opportunity to use the SCSI during a disk-disk backup >where the IDE was noticible (making the system sluggish). > >SCSI is a lot more cost-and-hassle than IDE, I'll do it if there is a clear >benefit vs hearsay, but it's hard to find someone to say > >I used to use IDE and when I changed to SCSI these marvelous things happened > >rather than > >I've made up my mind about SCSI, please don't try to confuse me with facts > >so please ... >James
[ DISCLAIMER: stated statistics are from memory, but are in the ballpark ] Benchmarks such as "hdparm -t -T /dev/drive" do not show the difference between SCSI and IDE. I once had the chance to help debug a decent server with a fast UDMA 100 IDE drive that was falling over dead at about 15 concurrent sessions. We slapped in an _OLD_ ULTRA2 SCSI drive and it ran ok with 30 concurrent sessions. [actually, it is still running fine on the old SCSI drive, I never asked for it back...] "hdparm -Tt" said that the IDE drive was twice as fast as the SCSI drive. bonnie++ (a hard drive benchmark utility) said that the IDE drive was somewhere around 30% faster than the SCSI drive. Yet the "slow" SCSI drive powered more than twice as many concurrent clients as the "fast" IDE drive. We put the IDE drive back in and added a second processor and more memory, without making much difference. The IDE drive was definately the bottleneck. Most of the hard drive utilities I've seen don't do a good job of stressing a hard drive in the same patterns that a terminal server does. IDE drives do a great job with linear access (such as tested by hdparm) but completely fall part when faced with a huge number of small, random reads and writes. Beyond a certain stress point, IDE drives just grind themselves to a halt. SCSI will decay gracefully. I've seen this many, many times. If IDE is currently working for you, great (but plan for it to fall apart if usage of terminal server increases). If you are trying to size a new server and are not sure whether to buy IDE or SCSI, go for SCSI. -Eric ------------------------------------------------------- This SF.net email is sponsored by: VM Ware With VMware you can run multiple operating systems on a single machine. WITHOUT REBOOTING! Mix Linux / Windows / Novell virtual machines at the same time. Free trial click here:http://www.vmware.com/wl/offer/358/0 _____________________________________________________________________ Ltsp-discuss mailing list. To un-subscribe, or change prefs, goto: https://lists.sourceforge.net/lists/listinfo/ltsp-discuss For additional LTSP help, try #ltsp channel on irc.freenode.net
