On Wed, 2006-09-27 at 18:21 +0300, Rafi Gordon wrote: > Hello, > > I made some more research on this topic. > > I am thinking of a solution using linux software RAID > for disk crash. > > > RAID 1 seems the best solution for this. (am I right?) > It works with disk mirroring. This means that the data is in fact > duplicated and written to both disks. This of course sets a high > load on the CPU and the data buses.
Unless you are using a -very- old machine (Pentium I/K5/K6), the CPU load should be virtually invisible. > > So my question is: > In practical terms, suppose we have 2 common 200 GB SATA-II disks (7200 RPM) > buffer size 8MB, and about 8-10 ms average seek time for read/write > (Or something like that). And suppose we have a 1GB RAM , on > x86 (not 64 bit) with about 3GHZ CPU clock. IMHO, I'd get a third 200GB disk and use RAID5. (Creating a second small RAID1 setup just for /boot) You should get better (read) performance at the price of a (slightly) higher CPU load on write. > > And suppose we are NOT talking about servers but of a > common linux programmer environment. (But on which a disk > crash is unbearable and there is management which may afford > another disk for that withouth hesitating). All my development workstations (Both @work and @home) use a 3/4 disk RAID5 configurations. In the past I had a number of IDE and SCSI disk crashes and the machines never lost a heartbeat. At most, I suffered from a minor performance degradation while the array was being rebuilt in the background. > > Will it be bearable to use such a solution ? Sure. > > Or will the machine be so slow that it will be unbearable ? Running on a 3.0Ghz CPU? You won't notice the RAID - even under severe I/O and CPU loads. > > I simply cannot test Linux RAID 1 performance because > it invloves erasing data and formattin to create a > RAID set. I just ran a short test (using hdparm) on one of my workstations (which uses a 4 x 80GB 7.2K IDE setup): /dev/md0: (/boot, 200MB) Timing cached reads: 2552 MB in 2.00 seconds = 1276.89 MB/sec Timing buffered disk reads: 98 MB in 2.03 seconds = 48.28 MB/sec /dev/md1: (root, ~12GB) Timing cached reads: 2848 MB in 2.00 seconds = 1423.99 MB/sec Timing buffered disk reads: 296 MB in 3.01 seconds = 98.46 MB/sec While hdparm is a poor benchmark tool, the 50MB/s (on the RAID1 based boot) is fairly close to the maximum throughput of older 80GB IDE100 drives. In short, you should expect better performance out of two 200GB SATA drives. Gilboa ================================================================= To unsubscribe, send mail to [EMAIL PROTECTED] with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail [EMAIL PROTECTED]
