From: CSBVAX::MRGATE!RELAY-INFO-VAX@CRVAX.SRI.COM@SMTP 13-SEP-1988 17:45 To: ARISIA::EVERHART Subj: Report on Using DigiData's Gigastore VHS tape system Received: From KL.SRI.COM by CRVAX.SRI.COM with TCP; Tue, 13 SEP 88 06:13:52 PDT Received: from LBL.Gov by KL.SRI.COM with TCP; Tue, 13 Sep 88 06:04:16 PDT Received: from warner.hepnet by LBL.Gov with VMSmail ; Tue, 13 Sep 88 05:59:27 PDT Date: Tue, 13 Sep 88 05:59:27 PDT From: nagy%warner.hepnet@LBL.Gov (Frank J. Nagy, VAX Wizard & Guru) Message-Id: <880913055927.21a03a11@LBL.Gov> Subject: Report on Using DigiData's Gigastore VHS tape system To: Info-VAX@kl.sri.com X-ST-Vmsmail-To: INFO_VAX,NAGY We have had a pair of DigiData Gigastores installed since Nov '87. Each drive is connected to a MicroVAX-II; these two MicroVAX-IIs are the boot nodes for an LAVC with (currently) 20 nodes. The system disks and the current main file store is a set of 4 RA81s (2 RA81s on each boot node). We do completely unattended nightly backup operations. A pair of batch jobs do BACKUP /IMAGE of the local RA81s to each Gigastore each night (by local, I mean that the RA81s directly connected to the MicroVAX-II the batch job is running on are the RA81s saved to that MicroVAX's Gigastore). Currently we are saving a total of about 1.1 GBytes (excluding page/swap files, etc.). The jobs take about 2 hours and 15 minutes to 2 1/2 hours (consistent with a average data rate of 60-65 KBytes/second - limited by BACKUP's throughput). Since these jobs are unattended (we just change the cassettes in the morning), their run time is of no concern to us. The backup command qualifiers used on our nightly jobs are: /Image - full disk backup /Ignore=Interlock - done online (system mostly idle) /Buffer=5 - buffering to keep Gigastores streaming /Block=32768 - big blocks give best Gigastore performance /NoCrc - needed for performance on MicroVAX-II or -3000 else CPU 100% saturated /Group=0 - Gigastore has *lots* of ECC /Journal= - So we can find the files later for users /Record - We also do incrementals at 12:00 and 18:00 to a pair of TK50s The /Buffer, /Block and /NoCrc are very important for use in order to get reasonable performance out of the Gigastores and MicroVAX-IIs (the /NoCrc is needed since the MicroVAX-II and -3000s emulate the CRC instruction causing severe CPU bottlenecks). We have had *no* media problems (we use Sony Pro-X T120 VHS cassettes) and have had *no* problems restoring selected files (for users) from old tapes. We don't worry about using the /NoCrc since the Gigastore is designed for backup and has an extensive amount of ECC (single bit error rate quoted as 1 in 10**23 as opposed to 1 in 10**13 quoted for TK50s). If BACKUP ever gets its *fast* CRC algorithm installed (apparently its coded and much faster than the emulated CRC instruction), we would probably begin to use /Crc once more. We have had few problems with the drives themselves. One drive was replaced in early Jan '88 due to problems with it going offline (the new drive had more recent firmware). Since then we've had only one problem which was resolved by running a cleaner cartridge through the drive (DigiData recommends *against* cleaning the drives on a regular basis since this disturbs their internal calibrations and will likely result in poor performance and undesireable consumption of tape, i.e. X amount of data will now fit on more tape than before the cleaning). After cleaning the drive, we ran a day's worth of continuous saves (over and over) to recalibrate the drive; the problem (excessive tape consumption) has not returned. The Gigastore's emulate TS11s. Our subsystem uses Dilog controllers (don't remember which flavor) supplied from DigiData along with a modified TSDRIVER. The driver has been modified to support the MicroVAX-I (unimportant to us) and to length its timeouts for the Gigastore (no code changes are required for the Gigastore). A VMS V5 version of the driver is already available. Since we installed the Gigastore's at the standard TS11 addresses, we are able to use Standalone BACKUP with the Gigastores and have saved and restored (using S/A Backup) RA81s when needed with no problems. All in all, we are very happy with the Gigastores. They have definitely solved our problem with backups; consider the savings in personnel time to feed tapes to the system along! We plan to expand our disk system over the next 6-8 months (to around 5 GBytes total) and will probably buy a 3rd Gigastore to insure that we can still do totally unattended backups (yes, we have fit all 4 RA81s onto a single cassette with no problems. Given the modest average throughput of BACKUP, I'd estimate that a T120 cassette could hold between 1.8 and 2.0 GBytes of data saved with VMS BACKUP). On the other hand, our new systems will all be using 8mm Exabyte systems (probably from Summus Computers). We have several of these on order already and plan to put one on our on LAVC (with the Gigastores) for media interchange and to build system install kits for use on systems with only the 8mm drives (emulating TK50s) as load media. However, we will apply similar procedures for unattended backup to using the 8mm tapes as we have developed for the Gigastores. We have no plans (at this time) to replace the Gigastores and remain happy owners and users. = Frank J. Nagy "VAX Guru & Wizard" = Fermilab Research Division EED/Controls = HEPNET: WARNER::NAGY (43198::NAGY) or FNAL::NAGY (43009::NAGY) = BitNet: NAGY@FNAL = USnail: Fermilab POB 500 MS/220 Batavia, IL 60510