If I setup a dedicated server with 15k SAS and 7.2k SATA disk together, SATA disk will be mounted as a backup volume and no system file on it. It will be used as a storage for backup only. Will SATA noticeably slow down the whole system? Thanks.
Not during normal operations. The only "slow down" you will see is that SATA can't write as fast as SAS can read during your backup, but if you're gzipping the backup files then CPU is usually the bottleneck not disk write speeds anyway.
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