lst_ho...@kwsoft.de put forth on 6/22/2010 6:50 AM: > Zitat von Ram <r...@netcore.co.in>:
>> Does that mean I can have them over different partitions on different >> disks. I had initially assumed all the postfix spool must be on the >> same partition > > From my understanding the spool must be on the same partition. The > "different disks" is meant to be RAID 0/1/10 whatever or a seperate disk > for the spool. This isn't even fully correct. Replace the word "partition" with "filesystem". Postfix has no knowledge of disk provisioning, whether partitions, or logical volumes created by some like LVM, etc. Postfix reads from and writes to a filesystem, period. The suggestion in the documentation assumes the reader is educated with respect to *nix disk subsystems and filesystems. The suggestion is to create a filesystem on a partition or logical volume on a disk subsystem comprised of multiple disks and some form of striping to increase read/write throughput. Striping allows read/write to multiple disk simultaneously. One would put the postfix spool directory on the resulting filesystem. In order of maximal performance the preferred striping RAID level would be: 1. RAID 0 2. RAID 10 3. RAID 5 4. RAID 50 5. RAID 6 RAID 0 decreases reliability but has vastly superior performance. If one disk fails, both fail, from the OS's perspective. 2-5 all offer increased reliability but 3-5 have decreased performance due to parity calculations, especially so for RAID 6 which calculates parity _twice_. My advice would be to only use 3-5 on a good hardware RAID controller with 256MB or more of cache. Due to performance vs reliability factors, my recommendation would be to use 4 drives in a software or hardware RAID 10, preferably 10k or 15k RPM drives of the SCSI or SAS flavor. SATA will work also but will be 30% to 100% slower. >From what the OP states, I'd say he'd probably do best with at least 73GB drives, which would yield 146GB of RAID 10 storage for the spool. This will yield twice the throughput of a single disk with double or more the reliability. RAID 10 can suffer two disk failures simultaneously, but they must be the "right" two disks because of the way the striping and mirroring is performed. Normally one would simply count on RAID 10 to gracefully suffer one disk failure, just like a mirrored set. -- Stan
