The SCSI TekRAM cards work great. I've been using them quite a bit over the last few months. Linux supports them very well, they support tagged queueing, and are very reliable. You can get better performance out of single DB storage systems like Zope, by striping the DB across multiple drives. You are basically limited to only 2 drives on IDE, because of the master/slave limitations. Redundancy, can also be added by mirroring across the striped drives. You can stripe across SCSI disks more efficiently. I've done some simple IDE RAID 1+0 mirrors and they do help the read performance, if the drives are on seperate IDE interfaces (both masters), but you pay on the writes, since you need to write to two drives instead of one. Scott Boyd On Mon, 15 Nov 1999, Sam Gendler wrote:
The biggest issue with SCSI is not so much performance any longer, but reliability. IDE drives have been traditionally targeted at the consumer market, while SCSI drives are aimed at the professional/server market. If you look at the Mean Time Between Failures numbers for the two types, SCSI tends to have been designed for higher reliability. That said, however, I have only ever had 2 IDE drives go south on me, with 0 scsi over the course of about 10 years. Those numbers are close enough for me, usually. Drive throughput tends to not be a huge issue with webservers, since servers spend most of their time seeking from one small object to another, not streaming enormous files to a network socket. With seek times anywhere between 8-14ms, and average object size somewhere around 8-15KB, if every object requires only one seek and one read from the disk, you can still only get about 70 transactions/second (assuming the read is instantaneous, which it isn't), which is only about 1 MB/second throughput. Therefore, it is much better to use multiple, slower drives, and distribute objects across multiple machines. Unfortunately, the data in zope is all stored in a single file, so this cannot be done. RAID is not much of a win, either, since raid increases throughput, but does nothing to improve seek time (it might even make it worse). You will be MUCH better off with more memory for buffering objects, to prevent disk access at all, rather than a fast drive.
On a zope-dev note, I have a variety of solutions that would allow zope to distribute objects across multiple physical hard drives, that should not be too difficult to implement, if anyone is interested. I don't have time to play with such concepts myself until next year.
--sam
tommy_b@my-deja.com wrote:
Oops, I'm going to use LINUX as the host OS.
I've done a bit of research on using SCSI. IWill & Tekram put out SCSI3 cards under $70 (according to http://www.pricewatch.com). Anyone use these guys? However, I'm not sure a cheap/close-out SCSI drive will match the performance-to-value ratio to a new ATA-66. http://www.storagereview.com has lots of drive tests that leads me to this thought. If I was spending more than $1000 for a new system, I'd go SCSI for sure. I need to keep below $700, but SCSI is one of my first planned upgrades. Is SCSI worth me getting a old used system with 64MB of RAM & slapping a SCSI card into it, or should I go for a new (dual) Celeron with 128MB?
Has anyone actually done performce tests with Zope & SQL to compare what component has the most impact for a _cheap_ system: CPU, memory, or HD throughput (ATA vs SCSI)?
Thanks for Stephan, Jim, & Nitin for the replies! --
On Sun, 14 Nov 1999 18:28:56 Nitin Borwankar wrote in "Re: [Zope] What to buy for cheap Zope host?":
tommy_b@my-deja.com wrote:
I'm building a computer to train & test Zope. I hope to use PostgreSQL or MySQL for storing a good-sized database. Zope would be used for allowing users to enter data & for output of formated querries. I wish to spend no more than $700 on this new computer I'm building (not including sound & video card + monitor). What should I spend the most money on, CPU, memory, HD, or a balance? I'm leaning towards a PPGA Celeron 366 (possibly overclocked), buying a 128MB stick of P100 RAM, and the fastest ATA drive $120 can buy. Is this the right direction? Ram's rather expencive now, or else I'd get 256MB right away.
In either case spending some money and getting a SCSI controller and drive gives a measurable contribution to performance. However this may take you into the next price point segment ~1000$. I have found there are good bargains on SCSI drives to be had on eBay and ONSALE auctions - go for new and 7200RPM or more.
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